hooks.txt: Use "array" in a sentence instead of `[]`

[lhc/web/wiklou.git] / docs / hooks.txt

hooks.txt

This document describes how event hooks work in MediaWiki; how to add hooks for
an event; and how to run hooks for an event.

==Glossary==

event
     Something that happens with the wiki. For example: a user logs in. A wiki
     page is saved. A wiki page is deleted. Often there are two events
     associated with a single action: one before the code is run to make the
     event happen, and one after. Each event has a name, preferably in
     CamelCase. For example, 'UserLogin', 'PageContentSave',
     'PageContentSaveComplete', 'ArticleDelete'.

hook
     A clump of code and data that should be run when an event happens. This can
     be either a function and a chunk of data, or an object and a method.

hook function
     The function part of a hook.

==Rationale==

Hooks allow us to decouple optionally-run code from code that is run for
everyone. It allows MediaWiki hackers, third-party developers and local
administrators to define code that will be run at certain points in the mainline
code, and to modify the data run by that mainline code. Hooks can keep mainline
code simple, and make it easier to write extensions. Hooks are a principled
alternative to local patches.

Consider, for example, two options in MediaWiki. One reverses the order of a
title before displaying the article; the other converts the title to all
uppercase letters. Currently, in MediaWiki code, we would handle this as follows
(note: not real code, here):

        function showAnArticle( $article ) {
                global $wgReverseTitle, $wgCapitalizeTitle;

                if ( $wgReverseTitle ) {
                        wfReverseTitle( $article );
                }

                if ( $wgCapitalizeTitle ) {
                        wfCapitalizeTitle( $article );
                }

                # code to actually show the article goes here
        }

An extension writer, or a local admin, will often add custom code to the
function -- with or without a global variable. For example, someone wanting
email notification when an article is shown may add:

        function showAnArticle( $article ) {
                global $wgReverseTitle, $wgCapitalizeTitle, $wgNotifyArticle;

                if ( $wgReverseTitle ) {
                        wfReverseTitle( $article );
                }

                if ( $wgCapitalizeTitle ) {
                        wfCapitalizeTitle( $article );
                }

                # code to actually show the article goes here

                if ( $wgNotifyArticle ) {
                        wfNotifyArticleShow( $article );
                }
        }

Using a hook-running strategy, we can avoid having all this option-specific
stuff in our mainline code. Using hooks, the function becomes:

        function showAnArticle( $article ) {
                if ( Hooks::run( 'ArticleShow', [ &$article ] ) ) {
                        # code to actually show the article goes here

                        Hooks::run( 'ArticleShowComplete', [ &$article ] );
                }
        }

We've cleaned up the code here by removing clumps of weird, infrequently used
code and moving them off somewhere else. It's much easier for someone working
with this code to see what's _really_ going on, and make changes or fix bugs.

In addition, we can take all the code that deals with the little-used
title-reversing options (say) and put it in one place. Instead of having little
title-reversing if-blocks spread all over the codebase in showAnArticle,
deleteAnArticle, exportArticle, etc., we can concentrate it all in an extension
file:

        function reverseArticleTitle( $article ) {
                # ...
        }

        function reverseForExport( $article ) {
                # ...
        }

The setup function for the extension just has to add its hook functions to the
appropriate events:

        setupTitleReversingExtension() {
                global $wgHooks;

                $wgHooks['ArticleShow'][] = 'reverseArticleTitle';
                $wgHooks['ArticleDelete'][] = 'reverseArticleTitle';
                $wgHooks['ArticleExport'][] = 'reverseForExport';
        }

Having all this code related to the title-reversion option in one place means
that it's easier to read and understand; you don't have to do a grep-find to see
where the $wgReverseTitle variable is used, say.

If the code is well enough isolated, it can even be excluded when not used --
making for some slight savings in memory and load-up performance at runtime.
Admins who want to have all the reversed titles can add:

        require_once 'extensions/ReverseTitle.php';

...to their LocalSettings.php file; those of us who don't want or need it can
just leave it out.

The extensions don't even have to be shipped with MediaWiki; they could be
provided by a third-party developer or written by the admin him/herself.

==Writing hooks==

A hook is a chunk of code run at some particular event. It consists of:

  * a function with some optional accompanying data, or
  * an object with a method and some optional accompanying data.

Hooks are registered by adding them to the global $wgHooks array for a given
event. All the following are valid ways to define hooks:

        $wgHooks['EventName'][] = 'someFunction'; # function, no data
        $wgHooks['EventName'][] = [ 'someFunction', $someData ];
        $wgHooks['EventName'][] = [ 'someFunction' ]; # weird, but OK

        $wgHooks['EventName'][] = $object; # object only
        $wgHooks['EventName'][] = [ $object, 'someMethod' ];
        $wgHooks['EventName'][] = [ $object, 'someMethod', $someData ];
        $wgHooks['EventName'][] = [ $object ]; # weird but OK

When an event occurs, the function (or object method) will be called with the
optional data provided as well as event-specific parameters. The above examples
would result in the following code being executed when 'EventName' happened:

        # function, no data
        someFunction( $param1, $param2 )
        # function with data
        someFunction( $someData, $param1, $param2 )

        # object only
        $object->onEventName( $param1, $param2 )
        # object with method
        $object->someMethod( $param1, $param2 )
        # object with method and data
        $object->someMethod( $someData, $param1, $param2 )

Note that when an object is the hook, and there's no specified method, the
default method called is 'onEventName'. For different events this would be
different: 'onArticleSave', 'onUserLogin', etc.

The extra data is useful if we want to use the same function or object for
different purposes. For example:

        $wgHooks['PageContentSaveComplete'][] = [ 'ircNotify', 'TimStarling' ];
        $wgHooks['PageContentSaveComplete'][] = [ 'ircNotify', 'brion' ];

This code would result in ircNotify being run twice when an article is saved:
once for 'TimStarling', and once for 'brion'.

Hooks can return three possible values:

  * No return value (or null): the hook has operated successfully. Previously,
    true was required. This is the default since MediaWiki 1.23.
  * "some string": an error occurred; processing should stop and the error
                   should be shown to the user
  * false: the hook has successfully done the work necessary and the calling
           function should skip

The last result would be for cases where the hook function replaces the main
functionality. For example, if you wanted to authenticate users to a custom
system (LDAP, another PHP program, whatever), you could do:

        $wgHooks['UserLogin'][] = [ 'ldapLogin', $ldapServer ];

        function ldapLogin( $username, $password ) {
                # log user into LDAP
                return false;
        }

Returning false makes less sense for events where the action is complete, and
will normally be ignored.

Note that none of the examples made use of create_function() as a way to
attach a function to a hook. This is known to cause problems (notably with
Special:Version), and should be avoided when at all possible.

==Using hooks==

A calling function or method uses the Hooks::run() function to run the hooks
related to a particular event, like so:

        class Article {
                # ...
                function protect() {
                        global $wgUser;

                        // Avoid PHP 7.1 warning from passing $this by reference
                        $article = $this;

                        if ( Hooks::run( 'ArticleProtect', [ &$article, &$wgUser ] ) ) {
                                # protect the article
                                Hooks::run( 'ArticleProtectComplete', [ &$article, &$wgUser ] );
                        }
                }
        }

Hooks::run() returns true if the calling function should continue processing
(the hooks ran OK, or there are no hooks to run), or false if it shouldn't (an
error occurred, or one of the hooks handled the action already). Checking the
return value matters more for "before" hooks than for "complete" hooks.

Hooks::run() was added in MediaWiki 1.18, before that the global function
wfRunHooks must be used, which was deprecated in MediaWiki 1.25.

Note that hook parameters are passed in an array; this is a necessary
inconvenience to make it possible to pass reference values (that can be changed)
into the hook code. Also note that earlier versions of wfRunHooks took a
variable number of arguments; the array calling protocol came about after
MediaWiki 1.4rc1.

==Events and parameters==

This is a list of known events and parameters; please add to it if you're going
to add events to the MediaWiki code.

'AbortAutoAccount': DEPRECATED since 1.27! Create a PreAuthenticationProvider
instead. Return false to cancel automated local account creation, where normally
authentication against an external auth plugin would be creating a local
account.
$user: the User object about to be created (read-only, incomplete)
&$abortMsg: out parameter: name of error message to be displayed to user

'AbortAutoblock': Return false to cancel an autoblock.
$autoblockip: The IP going to be autoblocked.
&$block: The block from which the autoblock is coming.

'AbortDiffCache': Can be used to cancel the caching of a diff.
&$diffEngine: DifferenceEngine object

'AbortEmailNotification': Can be used to cancel email notifications for an edit.
$editor: The User who made the change.
$title: The Title of the page that was edited.
$rc: The current RecentChange object.

'AbortLogin': DEPRECATED since 1.27! Create a PreAuthenticationProvider instead.
Return false to cancel account login.
$user: the User object being authenticated against
$password: the password being submitted, not yet checked for validity
&$retval: a LoginForm class constant to return from authenticateUserData();
  default is LoginForm::ABORTED. Note that the client may be using a machine
  API rather than the HTML user interface.
&$msg: the message identifier for abort reason (new in 1.18, not available
  before 1.18)

'AbortNewAccount': DEPRECATED since 1.27! Create a PreAuthenticationProvider
instead. Return false to cancel explicit account creation.
$user: the User object about to be created (read-only, incomplete)
&$msg: out parameter: HTML to display on abort
&$status: out parameter: Status object to return, replaces the older $msg param
  (added in 1.23)
  Create the object with Status::newFatal() to ensure proper API error
  messages are returned when creating account through API clients.

'AbortTalkPageEmailNotification': Return false to cancel talk page email
notification
$targetUser: the user whom to send talk page email notification
$title: the page title

'ActionBeforeFormDisplay': Before executing the HTMLForm object.
$name: name of the action
&$form: HTMLForm object
$article: Article object

'ActionModifyFormFields': Before creating an HTMLForm object for a page action;
Allows to change the fields on the form that will be generated.
$name: name of the action
&$fields: HTMLForm descriptor array
$article: Article object

'AddNewAccount': DEPRECATED since 1.27! Use LocalUserCreated.
After a user account is created.
$user: the User object that was created. (Parameter added in 1.7)
$byEmail: true when account was created "by email" (added in 1.12)

'AfterBuildFeedLinks': Executed in OutputPage.php after all feed links (atom,
rss,...) are created. Can be used to omit specific feeds from being outputted.
You must not use this hook to add feeds, use OutputPage::addFeedLink() instead.
&$feedLinks: Array of created feed links

'AfterFinalPageOutput': Nearly at the end of OutputPage::output() but
before OutputPage::sendCacheControl() and final ob_end_flush() which
will send the buffered output to the client. This allows for last-minute
modification of the output within the buffer by using ob_get_clean().
$output: The OutputPage object where output() was called

'AfterImportPage': When a page import is completed.
$title: Title under which the revisions were imported
$foreignTitle: ForeignTitle object based on data provided by the XML file
$revCount: Number of revisions in the XML file
$sRevCount: Number of successfully imported revisions
$pageInfo: associative array of page information

'AfterParserFetchFileAndTitle': After an image gallery is formed by Parser,
just before adding its HTML to parser output.
$parser: Parser object that called the hook
$ig: Gallery, an object of one of the gallery classes (inheriting from
  ImageGalleryBase)
&$html: HTML generated by the gallery

'AlternateEdit': Before checking if a user can edit a page and before showing
the edit form ( EditPage::edit() ). This is triggered on &action=edit.
$editPage: the EditPage object

'AlternateEditPreview': Before generating the preview of the page when editing
( EditPage::getPreviewText() ).
Return false and set $previewHTML and $parserOutput to output custom page
preview HTML.
$editPage: the EditPage object
&$content: the Content object for the text field from the edit page
&$previewHTML: Text to be placed into the page for the preview
&$parserOutput: the ParserOutput object for the preview

'AlternateUserMailer': Called before mail is sent so that mail could be logged
(or something else) instead of using PEAR or PHP's mail(). Return false to skip
the regular method of sending mail.  Return a string to return a php-mail-error
message containing the error. Returning true will continue with sending email
in the regular way.
$headers: Associative array of headers for the email
$to: MailAddress object or array
$from: From address
$subject: Subject of the email
$body: Body of the message

'APIAfterExecute': After calling the execute() method of an API module. Use
this to extend core API modules.
&$module: Module object

'ApiBeforeMain': Before calling ApiMain's execute() method in api.php.
&$main: ApiMain object

'ApiCheckCanExecute': Called during ApiMain::checkCanExecute. Use to further
authenticate and authorize API clients before executing the module. Return
false and set a message to cancel the request.
$module: Module object
$user: Current user
&$message: API message to die with. Specific values accepted depend on the
 MediaWiki version:
 * 1.29+: IApiMessage, Message, string message key, or key+parameters array to
   pass to ApiBase::dieWithError().
 * 1.27+: IApiMessage, or a key or key+parameters in ApiBase::$messageMap.
 * Earlier: A key or key+parameters in ApiBase::$messageMap.

'ApiDeprecationHelp': Add messages to the 'deprecation-help' warning generated
from ApiBase::addDeprecation().
&$msgs: Message[] Messages to include in the help. Multiple messages will be
  joined with spaces.

'APIEditBeforeSave': DEPRECATED since 1.28! Use EditFilterMergedContent instead.
Before saving a page with api.php?action=edit, after
processing request parameters. Return false to let the request fail, returning
an error message or an <edit result="Failure"> tag if $resultArr was filled.
Unlike for example 'EditFilterMergedContent' this also being run on undo.
Since MediaWiki 1.25, 'EditFilterMergedContent' can also return error details
for the API and it's recommended to use it instead of this hook.
$editPage: the EditPage object
$text: the text passed to the API. Note that this includes only the single
  section for section edit, and is not necessarily the final text in case of
  automatically resolved edit conflicts.
&$resultArr: data in this array will be added to the API result

'ApiFeedContributions::feedItem': Called to convert the result of ContribsPager
into a FeedItem instance that ApiFeedContributions can consume. Implementors of
this hook may cancel the hook to signal that the item is not viewable in the
provided context.
$row: A row of data from ContribsPager.  The set of data returned by
  ContribsPager can be adjusted by handling the ContribsPager::reallyDoQuery
  hook.
$context: An IContextSource implementation.
&$feedItem: Set this to a FeedItem instance if the callback can handle the
  provided row. This is provided to the hook as a null, if it is non null then
  another callback has already handled the hook.

'ApiFormatHighlight': Use to syntax-highlight API pretty-printed output. When
highlighting, add output to $context->getOutput() and return false.
$context: An IContextSource.
$text: Text to be highlighted.
$mime: MIME type of $text.
$format: API format code for $text.

'APIGetAllowedParams': Use this hook to modify a module's parameters.
&$module: ApiBase Module object
&$params: Array of parameters
$flags: int zero or OR-ed flags like ApiBase::GET_VALUES_FOR_HELP

'APIGetDescription': DEPRECATED since 1.25! Use APIGetDescriptionMessages
instead. Use this hook to modify a module's description.
&$module: ApiBase Module object
&$desc: String description, or array of description strings

'APIGetDescriptionMessages': Use this hook to modify a module's help message.
$module: ApiBase Module object
&$msg: Array of Message objects

'APIGetParamDescription': DEPRECATED since 1.25! Use
APIGetParamDescriptionMessages instead.
Use this hook to modify a module's parameter descriptions.
&$module: ApiBase Module object
&$desc: Array of parameter descriptions

'APIGetParamDescriptionMessages': Use this hook to modify a module's parameter
descriptions.
$module: ApiBase Module object
&$msg: Array of arrays of Message objects

'APIHelpModifyOutput': Use this hook to modify an API module's help output.
$module: ApiBase Module object
&$help: Array of HTML strings to be joined for the output.
$options: Array Options passed to ApiHelp::getHelp
&$tocData: Array If a TOC is being generated, this array has keys as anchors in
  the page and values as for Linker::generateTOC().

'ApiMain::moduleManager': Called when ApiMain has finished initializing its
module manager. Can be used to conditionally register API modules.
$moduleManager: ApiModuleManager Module manager instance

'ApiMain::onException': Called by ApiMain::executeActionWithErrorHandling() when
an exception is thrown during API action execution.
$apiMain: Calling ApiMain instance.
$e: Exception object.

'ApiMakeParserOptions': Called from ApiParse and ApiExpandTemplates to allow
extensions to adjust the ParserOptions before parsing.
$options: ParserOptions object
$title: Title to be parsed
$params: Parameter array for the API module
$module: API module (which is also a ContextSource)
&$reset: Set to a ScopedCallback used to reset any hooks after the parse is done.
&$suppressCache: Set true if cache should be suppressed.

'ApiOpenSearchSuggest': Called when constructing the OpenSearch results. Hooks
can alter or append to the array.
&$results: array with integer keys to associative arrays. Keys in associative
  array:
    - title: Title object.
    - redirect from: Title or null.
    - extract: Description for this result.
    - extract trimmed: If truthy, the extract will not be trimmed to
      $wgOpenSearchDescriptionLength.
    - image: Thumbnail for this result. Value is an array with subkeys 'source'
      (url), 'width', 'height', 'alt', 'align'.
    - url: Url for the given title.

'ApiParseMakeOutputPage': Called when preparing the OutputPage object for
ApiParse. This is mainly intended for calling OutputPage::addContentOverride()
or OutputPage::addContentOverrideCallback().
$module: ApiBase (which is also a ContextSource)
$output: OutputPage

'ApiQuery::moduleManager': Called when ApiQuery has finished initializing its
module manager. Can be used to conditionally register API query modules.
$moduleManager: ApiModuleManager Module manager instance

'APIQueryAfterExecute': After calling the execute() method of an
action=query submodule. Use this to extend core API modules.
&$module: Module object

'ApiQueryBaseAfterQuery': Called for (some) API query modules after the
database query has returned. An API query module wanting to use this hook
should see the ApiQueryBase::select() and ApiQueryBase::processRow()
documentation.
$module: ApiQueryBase module in question
$result: ResultWrapper|bool returned from the IDatabase::select()
&$hookData: array that was passed to the 'ApiQueryBaseBeforeQuery' hook and
  will be passed to the 'ApiQueryBaseProcessRow' hook, intended for inter-hook
  communication.

'ApiQueryBaseBeforeQuery': Called for (some) API query modules before a
database query is made. WARNING: It would be very easy to misuse this hook and
break the module! Any joins added *must* join on a unique key of the target
table unless you really know what you're doing. An API query module wanting to
use this hook should see the ApiQueryBase::select() and
ApiQueryBase::processRow() documentation.
$module: ApiQueryBase module in question
&$tables: array of tables to be queried
&$fields: array of columns to select
&$conds: array of WHERE conditionals for query
&$query_options: array of options for the database request
&$join_conds: join conditions for the tables
&$hookData: array that will be passed to the 'ApiQueryBaseAfterQuery' and
  'ApiQueryBaseProcessRow' hooks, intended for inter-hook communication.

'ApiQueryBaseProcessRow': Called for (some) API query modules as each row of
the database result is processed. Return false to stop processing the result
set. An API query module wanting to use this hook should see the
ApiQueryBase::select() and ApiQueryBase::processRow() documentation.
$module: ApiQueryBase module in question
$row: stdClass Database result row
&$data: array to be included in the ApiResult.
&$hookData: array that was be passed to the 'ApiQueryBaseBeforeQuery' and
  'ApiQueryBaseAfterQuery' hooks, intended for inter-hook communication.

'APIQueryGeneratorAfterExecute': After calling the executeGenerator() method of
an action=query submodule. Use this to extend core API modules.
&$module: Module object
&$resultPageSet: ApiPageSet object

'APIQueryInfoTokens': DEPRECATED since 1.24! Use ApiQueryTokensRegisterTypes
instead. Use this hook to add custom tokens to prop=info. Every token has an
action, which will be used in the intoken parameter and in the output
(actiontoken="..."), and a callback function which should return the token, or
false if the user isn't allowed to obtain it. The prototype of the callback
function is func($pageid, $title), where $pageid is the page ID of the page the
token is requested for and $title is the associated Title object. In the hook,
just add your callback to the $tokenFunctions array and return true (returning
false makes no sense).
&$tokenFunctions: [ action => callback ]

'APIQueryRecentChangesTokens': DEPRECATED since 1.24! Use
ApiQueryTokensRegisterTypes instead.
Use this hook to add custom tokens to list=recentchanges. Every token has an
action, which will be used in the rctoken parameter and in the output
(actiontoken="..."), and a callback function which should return the token, or
false if the user isn't allowed to obtain it. The prototype of the callback
function is func($pageid, $title, $rc), where $pageid is the page ID of the
page associated to the revision the token is requested for, $title the
associated Title object and $rc the associated RecentChange object. In the
hook, just add your callback to the $tokenFunctions array and return true
(returning false makes no sense).
&$tokenFunctions: [ action => callback ]

'APIQueryRevisionsTokens': DEPRECATED since 1.24! Use
ApiQueryTokensRegisterTypes instead.
Use this hook to add custom tokens to prop=revisions. Every token has an
action, which will be used in the rvtoken parameter and in the output
(actiontoken="..."), and a callback function which should return the token, or
false if the user isn't allowed to obtain it. The prototype of the callback
function is func($pageid, $title, $rev), where $pageid is the page ID of the
page associated to the revision the token is requested for, $title the
associated Title object and $rev the associated Revision object. In the hook,
just add your callback to the $tokenFunctions array and return true (returning
false makes no sense).
&$tokenFunctions: [ action => callback ]

'APIQuerySiteInfoGeneralInfo': Use this hook to add extra information to the
sites general information.
$module: the current ApiQuerySiteInfo module
&$results: array of results, add things here

'APIQuerySiteInfoStatisticsInfo': Use this hook to add extra information to the
sites statistics information.
&$results: array of results, add things here

'ApiQueryTokensRegisterTypes': Use this hook to add additional token types to
action=query&meta=tokens. Note that most modules will probably be able to use
the 'csrf' token instead of creating their own token types.
&$salts: [ type => salt to pass to User::getEditToken(), or array of salt
  and key to pass to Session::getToken() ]

'APIQueryUsersTokens': DEPRECATED since 1.24! Use ApiQueryTokensRegisterTypes
instead.
Use this hook to add custom token to list=users. Every token has an action,
which will be used in the ustoken parameter and in the output
(actiontoken="..."), and a callback function which should return the token, or
false if the user isn't allowed to obtain it. The prototype of the callback
function is func($user) where $user is the User object. In the hook, just add
your callback to the $tokenFunctions array and return true (returning false
makes no sense).
&$tokenFunctions: [ action => callback ]

'ApiQueryWatchlistExtractOutputData': Extract row data for ApiQueryWatchlist.
$module: ApiQueryWatchlist instance
$watchedItem: WatchedItem instance
$recentChangeInfo: Array of recent change info data
&$vals: Associative array of data to be output for the row

'ApiQueryWatchlistPrepareWatchedItemQueryServiceOptions': Populate the options
to be passed from ApiQueryWatchlist to WatchedItemQueryService.
$module: ApiQueryWatchlist instance
$params: Array of parameters, as would be returned by $module->extractRequestParams()
&$options: Array of options for WatchedItemQueryService::getWatchedItemsWithRecentChangeInfo()

'ApiRsdServiceApis': Add or remove APIs from the RSD services list. Each service
should have its own entry in the $apis array and have a unique name, passed as
key for the array that represents the service data. In this data array, the
key-value-pair identified by the apiLink key is required.
&$apis: array of services

'ApiTokensGetTokenTypes': DEPRECATED since 1.24! Use ApiQueryTokensRegisterTypes instead.
Use this hook to extend action=tokens with new token types.
&$tokenTypes: supported token types in format 'type' => callback function
  used to retrieve this type of tokens.

'ApiValidatePassword': Called from ApiValidatePassword.
$module: ApiValidatePassword instance.
&$r: Result array.

'Article::MissingArticleConditions': Before fetching deletion & move log entries
to display a message of a non-existing page being deleted/moved, give extensions
a chance to hide their (unrelated) log entries.
&$conds: Array of query conditions (all of which have to be met; conditions will
  AND in the final query)
$logTypes: Array of log types being queried

'ArticleAfterFetchContentObject': After fetching content of an article from the
database.
&$article: the article (object) being loaded from the database
&$content: the content of the article, as a Content object

'ArticleConfirmDelete': Before writing the confirmation form for article
deletion.
$article: the article (object) being deleted
$output: the OutputPage object
&$reason: the reason (string) the article is being deleted

'ArticleContentOnDiff': Before showing the article content below a diff. Use
this to change the content in this area or how it is loaded.
$diffEngine: the DifferenceEngine
$output: the OutputPage object

'ArticleContentViewCustom': Allows to output the text of the article in a
different format than wikitext. Note that it is preferable to implement proper
handing for a custom data type using the ContentHandler facility.
$content: content of the page, as a Content object
$title: title of the page
$output: reference to $wgOut

'ArticleDelete': Before an article is deleted.
&$wikiPage: the WikiPage (object) being deleted
&$user: the user (object) deleting the article
&$reason: the reason (string) the article is being deleted
&$error: if the deletion was prohibited, the (raw HTML) error message to display
  (added in 1.13)
&$status: Status object, modify this to throw an error. Overridden by $error
  (added in 1.20)
$suppress: Whether this is a suppression deletion or not (added in 1.27)

'ArticleDeleteAfterSuccess': Output after an article has been deleted.
$title: Title of the article that has been deleted.
$outputPage: OutputPage that can be used to append the output.

'ArticleDeleteComplete': After an article is deleted.
&$wikiPage: the WikiPage that was deleted
&$user: the user that deleted the article
$reason: the reason the article was deleted
$id: id of the article that was deleted
$content: the Content of the deleted page (or null, when deleting a broken page)
$logEntry: the ManualLogEntry used to record the deletion
$archivedRevisionCount: the number of revisions archived during the deletion

'ArticleEditUpdateNewTalk': Before updating user_newtalk when a user talk page
was changed.
&$wikiPage: WikiPage (object) of the user talk page
$recipient: User (object) who's talk page was edited

'ArticleEditUpdates': When edit updates (mainly link tracking) are made when an
article has been changed.
&$wikiPage: the WikiPage (object)
&$editInfo: data holder that includes the parser output ($editInfo->output) for
  that page after the change
$changed: bool for if the page was changed

'ArticleEditUpdatesDeleteFromRecentchanges': Before deleting old entries from
recentchanges table, return false to not delete old entries.
&$wikiPage: WikiPage (object) being modified

'ArticleFromTitle': when creating an article object from a title object using
Wiki::articleFromTitle().
&$title: Title (object) used to create the article object
&$article: Article (object) that will be returned
$context: IContextSource (object)

'ArticleMergeComplete': After merging to article using Special:Mergehistory.
$targetTitle: target title (object)
$destTitle: destination title (object)

'ArticlePageDataAfter': After loading data of an article from the database.
&$wikiPage: WikiPage (object) whose data were loaded
&$row: row (object) returned from the database server

'ArticlePageDataBefore': Before loading data of an article from the database.
&$wikiPage: WikiPage (object) that data will be loaded
&$fields: fields (array) to load from the database
&$tables: tables (array) to load from the database
&$joinConds: join conditions (array) to load from the database

'ArticlePrepareTextForEdit': Called when preparing text to be saved.
$wikiPage: the WikiPage being saved
$popts: parser options to be used for pre-save transformation

'ArticleProtect': Before an article is protected.
&$wikiPage: the WikiPage being protected
&$user: the user doing the protection
$protect: Set of restriction keys
$reason: Reason for protect

'ArticleProtectComplete': After an article is protected.
&$wikiPage: the WikiPage that was protected
&$user: the user who did the protection
$protect: Set of restriction keys
$reason: Reason for protect

'ArticlePurge': Before executing "&action=purge".
&$wikiPage: WikiPage (object) to purge

'ArticleRevisionUndeleted': After an article revision is restored.
&$title: the article title
$revision: the revision
$oldPageID: the page ID of the revision when archived (may be null)

'ArticleRevisionVisibilitySet': Called when changing visibility of one or more
revisions of an article.
$title: Title object of the article
$ids: Ids to set the visibility for
$visibilityChangeMap: Map of revision id to oldBits and newBits.  This array can be
  examined to determine exactly what visibility bits have changed for each
  revision.  This array is of the form
  [id => ['oldBits' => $oldBits, 'newBits' => $newBits], ... ]

'ArticleRollbackComplete': After an article rollback is completed.
$wikiPage: the WikiPage that was edited
$user: the user who did the rollback
$revision: the revision the page was reverted back to
$current: the reverted revision

'ArticleUndelete': When one or more revisions of an article are restored.
&$title: Title corresponding to the article restored
$create: Whether or not the restoration caused the page to be created (i.e. it
  didn't exist before).
$comment: The comment associated with the undeletion.
$oldPageId: ID of page previously deleted (from archive table). This ID will be used
  for the restored page.
$restoredPages: Set of page IDs that have revisions restored for this undelete,
  with keys being page IDs and values are 'true'.

'ArticleUndeleteLogEntry': When a log entry is generated but not yet saved.
$pageArchive: the PageArchive object
&$logEntry: ManualLogEntry object
$user: User who is performing the log action

'ArticleUpdateBeforeRedirect': After a page is updated (usually on save), before
the user is redirected back to the page.
$article: the article
&$sectionanchor: The section anchor link (e.g. "#overview" )
&$extraq: Extra query parameters which can be added via hooked functions

'ArticleViewFooter': After showing the footer section of an ordinary page view
$article: Article object
$patrolFooterShown: boolean whether patrol footer is shown

'ArticleViewHeader': Before the parser cache is about to be tried for article
viewing.
&$article: the article
&$pcache: whether to try the parser cache or not
&$outputDone: whether the output for this page finished or not. Set to
  a ParserOutput object to both indicate that the output is done and what
  parser output was used.

'ArticleViewRedirect': Before setting "Redirected from ..." subtitle when a
redirect was followed.
&$article: target article (object)

'AuthChangeFormFields': After converting a field information array obtained
from a set of AuthenticationRequest classes into a form descriptor; hooks
can tweak the array to change how login etc. forms should look.
$requests: array of AuthenticationRequests the fields are created from
$fieldInfo: field information array (union of all
  AuthenticationRequest::getFieldInfo() responses).
&$formDescriptor: HTMLForm descriptor. The special key 'weight' can be set
  to change the order of the fields.
$action: one of the AuthManager::ACTION_* constants.

'AuthManagerLoginAuthenticateAudit': A login attempt either succeeded or failed
for a reason other than misconfiguration or session loss. No return data is
accepted; this hook is for auditing only.
$response: The MediaWiki\Auth\AuthenticationResponse in either a PASS or FAIL
  state.
$user: The User object being authenticated against, or null if authentication
  failed before getting that far.
$username: A guess at the user name being authenticated, or null if we can't
  even determine that.

'AuthPluginAutoCreate': DEPRECATED since 1.27! Use the 'LocalUserCreated' hook
instead. Called when creating a local account for an user logged in from an
external authentication method.
$user: User object created locally

'AuthPluginSetup': DEPRECATED since 1.27! Extensions should be updated to use
AuthManager. Update or replace authentication plugin object ($wgAuth). Gives a
chance for an extension to set it programmatically to a variable class.
&$auth: the $wgAuth object, probably a stub

'AutopromoteCondition': Check autopromote condition for user.
$type: condition type
$args: arguments
$user: user
&$result: result of checking autopromote condition

'BacklinkCacheGetConditions': Allows to set conditions for query when links to
certain title are fetched.
$table: table name
$title: title of the page to which backlinks are sought
&$conds: query conditions

'BacklinkCacheGetPrefix': Allows to set prefix for a specific link table.
$table: table name
&$prefix: prefix

'BadImage': When checking against the bad image list. Change $bad and return
false to override. If an image is "bad", it is not rendered inline in wiki
pages or galleries in category pages.
$name: Image name being checked
&$bad: Whether or not the image is "bad"

'BaseTemplateAfterPortlet': After output of portlets, allow injecting
custom HTML after the section. Any uses of the hook need to handle escaping.
$template: BaseTemplate
$portlet: string portlet name
&$html: string

'BaseTemplateToolbox': Called by BaseTemplate when building the $toolbox array
and returning it for the skin to output. You can add items to the toolbox while
still letting the skin make final decisions on skin-specific markup conventions
using this hook.
&$sk: The BaseTemplate base skin template
&$toolbox: An array of toolbox items, see BaseTemplate::getToolbox and
  BaseTemplate::makeListItem for details on the format of individual items
  inside of this array.

'BeforeDisplayNoArticleText': Before displaying message key "noarticletext" or
"noarticletext-nopermission" at Article::showMissingArticle().
$article: article object

'BeforeHttpsRedirect': Prior to forcing HTTP->HTTPS redirect. Gives a chance to
override how the redirect is output by modifying, or by returning false, and
letting standard HTTP rendering take place.
ATTENTION: This hook is likely to be removed soon due to overall design of the
system.
$context: IContextSource object
&$redirect: string URL, modifiable

'BeforeInitialize': Before anything is initialized in
MediaWiki::performRequest().
&$title: Title being used for request
&$unused: null
&$output: OutputPage object
&$user: User
$request: WebRequest object
$mediaWiki: Mediawiki object

'BeforePageDisplay': Prior to outputting a page.
&$out: OutputPage object
&$skin: Skin object

'BeforePageRedirect': Prior to sending an HTTP redirect. Gives a chance to
override how the redirect is output by modifying, or by returning false and
taking over the output.
$out: OutputPage object
&$redirect: URL, modifiable
&$code: HTTP code (eg '301' or '302'), modifiable

'BeforeParserFetchFileAndTitle': Before an image is rendered by Parser.
$parser: Parser object
$nt: the image title
&$options: array of options to RepoGroup::findFile. If it contains 'broken'
  as a key then the file will appear as a broken thumbnail.
&$descQuery: query string to add to thumbnail URL

'BeforeParserFetchTemplateAndtitle': Before a template is fetched by Parser.
$parser: Parser object
$title: title of the template
&$skip: skip this template and link it?
&$id: the id of the revision being parsed

'BeforeParserrenderImageGallery': Before an image gallery is rendered by Parser.
&$parser: Parser object
&$ig: ImageGallery object

'BeforeWelcomeCreation': Before the welcomecreation message is displayed to a
newly created user.
&$welcome_creation_msg: MediaWiki message name to display on the welcome screen
  to a newly created user account.
&$injected_html: Any HTML to inject after the "logged in" message of a newly
  created user account

'BitmapHandlerCheckImageArea': By BitmapHandler::normaliseParams, after all
normalizations have been performed, except for the $wgMaxImageArea check.
$image: File
&$params: Array of parameters
&$checkImageAreaHookResult: null, set to true or false to override the
  $wgMaxImageArea check result.

'BitmapHandlerTransform': before a file is transformed, gives extension the
possibility to transform it themselves
$handler: BitmapHandler
$image: File
&$scalerParams: Array with scaler parameters
&$mto: null, set to a MediaTransformOutput

'BlockIp': Before an IP address or user is blocked.
&$block: the Block object about to be saved
&$user: the user _doing_ the block (not the one being blocked)
&$reason: if the hook is aborted, the error message to be returned in an array

'BlockIpComplete': After an IP address or user is blocked.
$block: the Block object that was saved
$user: the user who did the block (not the one being blocked)
$priorBlock: the Block object for the prior block or null if there was none

'BookInformation': Before information output on Special:Booksources.
$isbn: ISBN to show information for
$output: OutputPage object in use

'CanIPUseHTTPS': Determine whether the client at a given source IP is likely
to be able to access the wiki via HTTPS.
$ip: The IP address in human-readable form
&$canDo: This reference should be set to false if the client may not be able
  to use HTTPS

'CanonicalNamespaces': For extensions adding their own namespaces or altering
the defaults.
Note that if you need to specify namespace protection or content model for
a namespace that is added in a CanonicalNamespaces hook handler, you
should do so by altering $wgNamespaceProtection and
$wgNamespaceContentModels outside the handler, in top-level scope. The
point at which the CanonicalNamespaces hook fires is too late for altering
these variables. This applies even if the namespace addition is
conditional; it is permissible to declare a content model and protection
for a namespace and then decline to actually register it.
&$namespaces: Array of namespace numbers with corresponding canonical names

'CategoryAfterPageAdded': After a page is added to a category.
$category: Category that page was added to
$wikiPage: WikiPage that was added

'CategoryAfterPageRemoved': After a page is removed from a category.
$category: Category that page was removed from
$wikiPage: WikiPage that was removed
$id: the page ID (original ID in case of page deletions)

'CategoryPageView': Before viewing a categorypage in CategoryPage::view.
&$catpage: CategoryPage instance

'CategoryViewer::doCategoryQuery': After querying for pages to be displayed
in a Category page. Gives extensions the opportunity to batch load any
related data about the pages.
$type: The category type. Either 'page', 'file' or 'subcat'
$res: Query result from Wikimedia\Rdbms\IDatabase::select()

'CategoryViewer::generateLink': Before generating an output link allow
extensions opportunity to generate a more specific or relevant link.
$type: The category type. Either 'page', 'img' or 'subcat'
$title: Title object for the categorized page
$html: Requested html content of anchor
&$link: Returned value. When set to a non-null value by a hook subscriber
  this value will be used as the anchor instead of Linker::link

'ChangeAuthenticationDataAudit': Called when user changes his password.
No return data is accepted; this hook is for auditing only.
$req: AuthenticationRequest object describing the change (and target user)
$status: StatusValue with the result of the action

'ChangePasswordForm': DEPRECATED since 1.27! Use AuthChangeFormFields or
security levels. For extensions that need to add a field to the ChangePassword
form via the Preferences form.
&$extraFields: An array of arrays that hold fields like would be passed to the
  pretty function.

'ChangesListInitRows': Batch process change list rows prior to rendering.
$changesList: ChangesList instance
$rows: The data that will be rendered. May be a ResultWrapper instance or
  an array.

'ChangesListInsertArticleLink': Override or augment link to article in RC list.
&$changesList: ChangesList instance.
&$articlelink: HTML of link to article (already filled-in).
&$s: HTML of row that is being constructed.
&$rc: RecentChange instance.
$unpatrolled: Whether or not we are showing unpatrolled changes.
$watched: Whether or not the change is watched by the user.

'ChangesListSpecialPageFilters': DEPRECATED since 1.29! Use
'ChangesListSpecialPageStructuredFilters' instead.
Called after building form options on pages
inheriting from ChangesListSpecialPage (in core: RecentChanges,
RecentChangesLinked and Watchlist).
$special: ChangesListSpecialPage instance
&$filters: associative array of filter definitions. The keys are the HTML
  name/URL parameters. Each key maps to an associative array with a 'msg'
  (message key) and a 'default' value.

'ChangesListSpecialPageQuery': Called when building SQL query on pages
inheriting from ChangesListSpecialPage (in core: RecentChanges,
RecentChangesLinked and Watchlist).
Do not use this to implement individual filters if they are compatible with the
ChangesListFilter and ChangesListFilterGroup structure.
Instead, use sub-classes of those classes, in conjunction with the
ChangesListSpecialPageStructuredFilters hook.
This hook can be used to implement filters that do not implement that structure,
or custom behavior that is not an individual filter.
$name: name of the special page, e.g. 'Watchlist'
&$tables: array of tables to be queried
&$fields: array of columns to select
&$conds: array of WHERE conditionals for query
&$query_options: array of options for the database request
&$join_conds: join conditions for the tables
$opts: FormOptions for this request

'ChangesListSpecialPageStructuredFilters': Called to allow extensions to register
filters for pages inheriting from ChangesListSpecialPage (in core: RecentChanges,
RecentChangesLinked, and Watchlist).  Generally, you will want to construct
new ChangesListBooleanFilter or ChangesListStringOptionsFilter objects.
When constructing them, you specify which group they belong to.  You can reuse
existing groups (accessed through $special->getFilterGroup), or create your own
(ChangesListBooleanFilterGroup or ChangesListStringOptionsFilterGroup).
If you create new groups, you must register them with $special->registerFilterGroup.
Note that this is called regardless of whether the user is currently using
the new (structured) or old (unstructured) filter UI.  If you want your boolean
filter to show on both the new and old UI, specify all the supported fields.
These include showHide, label, and description.
See the constructor of each ChangesList* class for documentation of supported
fields.
$special: ChangesListSpecialPage instance

'ChangeTagAfterDelete': Called after a change tag has been deleted (that is,
removed from all revisions and log entries to which it was applied). This gives
extensions a chance to take it off their books.
$tag: name of the tag
&$status: Status object. Add warnings to this as required. There is no point
  setting errors, as the deletion has already been partly carried out by this
  point.

'ChangeTagCanCreate': Tell whether a change tag should be able to be created
from the UI (Special:Tags) or via the API. You could use this hook if you want
to reserve a specific "namespace" of tags, or something similar.
$tag: name of the tag
$user: user initiating the action
&$status: Status object. Add your errors using `$status->fatal()` or warnings
  using `$status->warning()`. Errors and warnings will be relayed to the user.
  If you set an error, the user will be unable to create the tag.

'ChangeTagCanDelete': Tell whether a change tag should be able to be
deleted from the UI (Special:Tags) or via the API. The default is that tags
defined using the ListDefinedTags hook are not allowed to be deleted unless
specifically allowed. If you wish to allow deletion of the tag, set
`$status = Status::newGood()` to allow deletion, and then `return false` from
the hook function. Ensure you consume the 'ChangeTagAfterDelete' hook to carry
out custom deletion actions.
$tag: name of the tag
$user: user initiating the action
&$status: Status object. See above.

'ChangeTagsListActive': Allows you to nominate which of the tags your extension
uses are in active use.
&$tags: list of all active tags. Append to this array.

'ChangeTagsAfterUpdateTags': Called after tags have been updated with the
ChangeTags::updateTags function. Params:
$addedTags: tags effectively added in the update
$removedTags: tags effectively removed in the update
$prevTags: tags that were present prior to the update
$rc_id: recentchanges table id
$rev_id: revision table id
$log_id: logging table id
$params: tag params
$rc: RecentChange being tagged when the tagging accompanies the action, or null
$user: User who performed the tagging when the tagging is subsequent to the
  action, or null

'ChangeTagsAllowedAdd': Called when checking if a user can add tags to a change.
&$allowedTags: List of all the tags the user is allowed to add. Any tags the
  user wants to add ($addTags) that are not in this array will cause it to fail.
  You may add or remove tags to this array as required.
$addTags: List of tags user intends to add.
$user: User who is adding the tags.

'ChangeUserGroups': Called before user groups are changed.
$performer: The User who will perform the change
$user: The User whose groups will be changed
&$add: The groups that will be added
&$remove: The groups that will be removed

'Collation::factory': Called if $wgCategoryCollation is an unknown collation.
$collationName: Name of the collation in question
&$collationObject: Null. Replace with a subclass of the Collation class that
  implements the collation given in $collationName.

'ConfirmEmailComplete': Called after a user's email has been confirmed
successfully.
$user: user (object) whose email is being confirmed

'ContentAlterParserOutput': Modify parser output for a given content object.
Called by Content::getParserOutput after parsing has finished. Can be used
for changes that depend on the result of the parsing but have to be done
before LinksUpdate is called (such as adding tracking categories based on
the rendered HTML).
$content: The Content to render
$title: Title of the page, as context
$parserOutput: ParserOutput to manipulate

'ContentGetParserOutput': Customize parser output for a given content object,
called by AbstractContent::getParserOutput. May be used to override the normal
model-specific rendering of page content.
$content: The Content to render
$title: Title of the page, as context
$revId: The revision ID, as context
$options: ParserOptions for rendering. To avoid confusing the parser cache,
  the output can only depend on parameters provided to this hook function, not
  on global state.
$generateHtml: boolean, indicating whether full HTML should be generated. If
  false, generation of HTML may be skipped, but other information should still
  be present in the ParserOutput object.
&$output: ParserOutput, to manipulate or replace

'ContentHandlerDefaultModelFor': Called when the default content model is
determined for a given title. May be used to assign a different model for that
title.
$title: the Title in question
&$model: the model name. Use with CONTENT_MODEL_XXX constants.

'ContentHandlerForModelID': Called when a ContentHandler is requested for
a given content model name, but no entry for that model exists in
$wgContentHandlers.
Note: if your extension implements additional models via this hook, please
use GetContentModels hook to make them known to core.
$modeName: the requested content model name
&$handler: set this to a ContentHandler object, if desired.

'ContentModelCanBeUsedOn': Called to determine whether that content model can
be used on a given page. This is especially useful to prevent some content
models to be used in some special location.
$contentModel: ID of the content model in question
$title: the Title in question.
&$ok: Output parameter, whether it is OK to use $contentModel on $title.
  Handler functions that modify $ok should generally return false to prevent
  further hooks from further modifying $ok.

'ContribsPager::getQueryInfo': Before the contributions query is about to run
&$pager: Pager object for contributions
&$queryInfo: The query for the contribs Pager

'ContribsPager::reallyDoQuery': Called before really executing the query for My
Contributions
&$data: an array of results of all contribs queries
$pager: The ContribsPager object hooked into
$offset: Index offset, inclusive
$limit: Exact query limit
$descending: Query direction, false for ascending, true for descending

'ContributionsLineEnding': Called before a contributions HTML line is finished
$page: SpecialPage object for contributions
&$ret: the HTML line
$row: the DB row for this line
&$classes: the classes to add to the surrounding <li>
&$attribs: associative array of other HTML attributes for the <li> element.
  Currently only data attributes reserved to MediaWiki are allowed
  (see Sanitizer::isReservedDataAttribute).

'ContributionsToolLinks': Change tool links above Special:Contributions
$id: User identifier
$title: User page title
&$tools: Array of tool links
$specialPage: SpecialPage instance for context and services. Can be either
  SpecialContributions or DeletedContributionsPage. Extensions should type
  hint against a generic SpecialPage though.

'ConvertContent': Called by AbstractContent::convert when a conversion to
another content model is requested.
Handler functions that modify $result should generally return false to disable
further attempts at conversion.
$content: The Content object to be converted.
$toModel: The ID of the content model to convert to.
$lossy:   boolean indicating whether lossy conversion is allowed.
&$result: Output parameter, in case the handler function wants to provide a
  converted Content object. Note that $result->getContentModel() must return
  $toModel.

'ContentSecurityPolicyDefaultSource': Modify the allowed CSP load sources. This
affects all directives except for the script directive. If you want to add a
script source, see ContentSecurityPolicyScriptSource hook.
&$defaultSrc: Array of Content-Security-Policy allowed sources
$policyConfig: Current configuration for the Content-Security-Policy header
$mode: ContentSecurityPolicy::REPORT_ONLY_MODE or
  ContentSecurityPolicy::FULL_MODE depending on type of header

'ContentSecurityPolicyDirectives': Modify the content security policy
directives. Use this only if ContentSecurityPolicyDefaultSource and
ContentSecurityPolicyScriptSource do not meet your needs.
&$directives: Array of CSP directives
$policyConfig: Current configuration for the CSP header
$mode: ContentSecurityPolicy::REPORT_ONLY_MODE or
  ContentSecurityPolicy::FULL_MODE depending on type of header

'ContentSecurityPolicyScriptSource': Modify the allowed CSP script sources.
Note that you also have to use ContentSecurityPolicyDefaultSource if you
want non-script sources to be loaded from
whatever you add.
&$scriptSrc: Array of CSP directives
$policyConfig: Current configuration for the CSP header
$mode: ContentSecurityPolicy::REPORT_ONLY_MODE or
  ContentSecurityPolicy::FULL_MODE depending on type of header

'CustomEditor': When invoking the page editor
Return true to allow the normal editor to be used, or false if implementing
a custom editor, e.g. for a special namespace, etc.
$article: Article being edited
$user: User performing the edit

'DatabaseOraclePostInit': Called after initialising an Oracle database
$db: the DatabaseOracle object

'DeletedContribsPager::reallyDoQuery': Called before really executing the query
for Special:DeletedContributions
Similar to ContribsPager::reallyDoQuery
&$data: an array of results of all contribs queries
$pager: The DeletedContribsPager object hooked into
$offset: Index offset, inclusive
$limit: Exact query limit
$descending: Query direction, false for ascending, true for descending

'DeletedContributionsLineEnding': Called before a DeletedContributions HTML line
is finished.
Similar to ContributionsLineEnding
$page: SpecialPage object for DeletedContributions
&$ret: the HTML line
$row: the DB row for this line
&$classes: the classes to add to the surrounding <li>
&$attribs: associative array of other HTML attributes for the <li> element.
  Currently only data attributes reserved to MediaWiki are allowed
  (see Sanitizer::isReservedDataAttribute).

'DeleteUnknownPreferences': Called by the cleanupPreferences.php maintenance
script to build a WHERE clause with which to delete preferences that are not
known about. This hook is used by extensions that have dynamically-named
preferences that should not be deleted in the usual cleanup process. For
example, the Gadgets extension creates preferences prefixed with 'gadget-', and
so anything with that prefix is excluded from the deletion.
&where: An array that will be passed as the $cond parameter to
  IDatabase::select() to determine what will be deleted from the user_properties
  table.
$db: The IDatabase object, useful for accessing $db->buildLike() etc.

'DifferenceEngineAfterLoadNewText': called in DifferenceEngine::loadNewText()
after the new revision's content has been loaded into the class member variable
$differenceEngine->mNewContent but before returning true from this function.
$differenceEngine: DifferenceEngine object

'DifferenceEngineLoadTextAfterNewContentIsLoaded': called in
DifferenceEngine::loadText() after the new revision's content has been loaded
into the class member variable $differenceEngine->mNewContent but before
checking if the variable's value is null.
This hook can be used to inject content into said class member variable.
$differenceEngine: DifferenceEngine object

'DifferenceEngineMarkPatrolledLink': Allows extensions to change the "mark as
patrolled" link which is shown both on the diff header as well as on the bottom
of a page, usually wrapped in a span element which has class="patrollink".
$differenceEngine: DifferenceEngine object
&$markAsPatrolledLink: The "mark as patrolled" link HTML (string)
$rcid: Recent change ID (rc_id) for this change (int)

'DifferenceEngineMarkPatrolledRCID': Allows extensions to possibly change the
rcid parameter. For example the rcid might be set to zero due to the user being
the same as the performer of the change but an extension might still want to
show it under certain conditions.
&$rcid: rc_id (int) of the change or 0
$differenceEngine: DifferenceEngine object
$change: RecentChange object
$user: User object representing the current user

'DifferenceEngineNewHeader': Allows extensions to change the $newHeader
variable, which contains information about the new revision, such as the
revision's author, whether the revision was marked as a minor edit or not, etc.
$differenceEngine: DifferenceEngine object
&$newHeader: The string containing the various #mw-diff-otitle[1-5] divs, which
  include things like revision author info, revision comment, RevisionDelete
  link and more
$formattedRevisionTools: Array containing revision tools, some of which may have
  been injected with the DiffRevisionTools hook
$nextlink: String containing the link to the next revision (if any); also
  included in $newHeader
$rollback: Rollback link (string) to roll this revision back to the previous
  one, if any
$newminor: String indicating if the new revision was marked as a minor edit
$diffOnly: Boolean parameter passed to DifferenceEngine#showDiffPage, indicating
  whether we should show just the diff; passed in as a query string parameter to
  the various URLs constructed here (i.e. $nextlink)
$rdel: RevisionDelete link for the new revision, if the current user is allowed
  to use the RevisionDelete feature
$unhide: Boolean parameter indicating whether to show RevisionDeleted revisions

'DifferenceEngineOldHeader': Allows extensions to change the $oldHeader
variable, which contains information about the old revision, such as the
revision's author, whether the revision was marked as a minor edit or not, etc.
$differenceEngine: DifferenceEngine object
&$oldHeader: The string containing the various #mw-diff-otitle[1-5] divs, which
  include things like revision author info, revision comment, RevisionDelete
  link and more
$prevlink: String containing the link to the previous revision (if any); also
  included in $oldHeader
$oldminor: String indicating if the old revision was marked as a minor edit
$diffOnly: Boolean parameter passed to DifferenceEngine#showDiffPage, indicating
  whether we should show just the diff; passed in as a query string parameter to
  the various URLs constructed here (i.e. $prevlink)
$ldel: RevisionDelete link for the old revision, if the current user is allowed
  to use the RevisionDelete feature
$unhide: Boolean parameter indicating whether to show RevisionDeleted revisions

'DifferenceEngineOldHeaderNoOldRev': Change the $oldHeader variable in cases
when there is no old revision
&$oldHeader: empty string by default

'DifferenceEngineRenderRevisionAddParserOutput': Allows extensions to change the
parser output. Return false to not add parser output via OutputPage's
addParserOutput method.
$differenceEngine: DifferenceEngine object
$out: OutputPage object
$parserOutput: ParserOutput object
$wikiPage: WikiPage object

'DifferenceEngineRenderRevisionShowFinalPatrolLink': An extension can hook into
this hook point and return false to not show the final "mark as patrolled" link
on the bottom of a page.
This hook has no arguments.

'DifferenceEngineShowDiff': Allows extensions to affect the diff text which
eventually gets sent to the OutputPage object.
$differenceEngine: DifferenceEngine object

'DifferenceEngineShowEmptyOldContent': Allows extensions to change the diff
table body (without header) in cases when there is no old revision or the old
and new revisions are identical.
$differenceEngine: DifferenceEngine object

'DifferenceEngineShowDiffPage': Add additional output via the available
OutputPage object into the diff view
$out: OutputPage object

'DifferenceEngineShowDiffPageMaybeShowMissingRevision': called in
DifferenceEngine::showDiffPage() when revision data cannot be loaded.
Return false in order to prevent displaying the missing revision message
(i.e. to prevent DifferenceEngine::showMissingRevision() from being called).
$differenceEngine: DifferenceEngine object

'DiffRevisionTools': Override or extend the revision tools available from the
diff view, i.e. undo, etc.
$newRev: Revision object of the "new" revision
&$links: Array of HTML links
$oldRev: Revision object of the "old" revision (may be null)
$user: Current user object

'DiffViewHeader': Called before diff display
$diff: DifferenceEngine object that's calling
$oldRev: Revision object of the "old" revision (may be null/invalid)
$newRev: Revision object of the "new" revision

'DisplayOldSubtitle': before creating subtitle when browsing old versions of
an article
&$article: article (object) being viewed
&$oldid: oldid (int) being viewed

'DoEditSectionLink': DEPRECATED since 1.25! Use SkinEditSectionLinks instead.
Override the HTML generated for section edit links
$skin: Skin object rendering the UI
$title: Title object for the title being linked to (may not be the same as
  the page title, if the section is included from a template)
$section: The designation of the section being pointed to, to be included in
  the link, like "&section=$section"
$tooltip: The default tooltip.  Escape before using.
  By default, this is wrapped in the 'editsectionhint' message.
&$result: The HTML to return, prefilled with the default plus whatever other
  changes earlier hooks have made
$lang: The language code to use for the link in the wfMessage function

'EditFilter': Perform checks on an edit
$editor: EditPage instance (object). The edit form (see includes/EditPage.php)
$text: Contents of the edit box
$section: Section being edited
&$error: Error message to return
$summary: Edit summary for page

'EditFilterMergedContent': Post-section-merge edit filter.
This may be triggered by the EditPage or any other facility that modifies page
content. Use the $status object to indicate whether the edit should be allowed,
and to provide a reason for disallowing it. Return false to abort the edit, and
true to continue. Returning true if $status->isOK() returns false means "don't
save but continue user interaction", e.g. show the edit form.
$status->apiHookResult can be set to an array to be returned by api.php
  action=edit. This is used to deliver captchas.
$context: object implementing the IContextSource interface.
$content: content of the edit box, as a Content object.
$status: Status object to represent errors, etc.
$summary: Edit summary for page
$user: the User object representing the user whois performing the edit.
$minoredit: whether the edit was marked as minor by the user.

'EditFormInitialText': Allows modifying the edit form when editing existing
pages
$editPage: EditPage object

'EditFormPreloadText': Allows population of the edit form when creating
new pages
&$text: Text to preload with
&$title: Title object representing the page being created

'EditPage::attemptSave': Called before an article is
saved, that is before WikiPage::doEditContent() is called
$editpage_Obj: the current EditPage object

'EditPage::attemptSave:after': Called after an article save attempt
$editpage_Obj: the current EditPage object
$status: the resulting Status object
$resultDetails: Result details array

'EditPage::importFormData': allow extensions to read additional data
posted in the form
Return value is ignored (should always return true)
$editpage: EditPage instance
$request: Webrequest

'EditPage::showEditForm:fields': allows injection of form field into edit form
Return value is ignored (should always return true)
&$editor: the EditPage instance for reference
&$out: an OutputPage instance to write to

'EditPage::showEditForm:initial': before showing the edit form
Return false to halt editing; you'll need to handle error messages, etc.
yourself. Alternatively, modifying $error and returning true will cause the
contents of $error to be echoed at the top of the edit form as wikitext.
Return true without altering $error to allow the edit to proceed.
&$editor: EditPage instance (object)
&$out: an OutputPage instance to write to

'EditPage::showReadOnlyForm:initial': similar to EditPage::showEditForm:initial
but for the read-only 'view source' variant of the edit form.
Return value is ignored (should always return true)
$editor: EditPage instance (object)
&$out: an OutputPage instance to write to

'EditPage::showStandardInputs:options': allows injection of form fields into
the editOptions area
Return value is ignored (should always be true)
$editor: EditPage instance (object)
$out: an OutputPage instance to write to
&$tabindex: HTML tabindex of the last edit check/button

'EditPageBeforeConflictDiff': allows modifying the EditPage object and output
when there's an edit conflict.  Return false to halt normal diff output; in
this case you're responsible for computing and outputting the entire "conflict"
part, i.e., the "difference between revisions" and "your text" headers and
sections.
&$editor: EditPage instance
&$out: OutputPage instance

'EditPageBeforeEditButtons': Allows modifying the edit buttons below the
textarea in the edit form.
&$editpage: The current EditPage object
&$buttons: Array of edit buttons "Save", "Preview", "Live", and "Diff"
&$tabindex: HTML tabindex of the last edit check/button

'EditPageBeforeEditToolbar': Allows modifying the edit toolbar above the
textarea in the edit form.
Hook subscribers can return false to avoid the default toolbar code being
loaded.
&$toolbar: The toolbar HTML

'EditPageCopyrightWarning': Allow for site and per-namespace customization of
contribution/copyright notice.
$title: title of page being edited
&$msg: localization message name, overridable. Default is either
  'copyrightwarning' or 'copyrightwarning2'.

'EditPageGetCheckboxesDefinition': Allows modifying the edit checkboxes
below the textarea in the edit form.
$editpage: The current EditPage object
&$checkboxes: Array of checkbox definitions. See
  EditPage::getCheckboxesDefinition() for the format.

'EditPageGetDiffContent': Allow modifying the wikitext that will be used in
"Show changes". Note that it is preferable to implement diff handling for
different data types using the ContentHandler facility.
$editPage: EditPage object
&$newtext: wikitext that will be used as "your version"

'EditPageGetPreviewContent': Allow modifying the wikitext that will be
previewed. Note that it is preferable to implement previews for different data
types using the ContentHandler facility.
$editPage: EditPage object
&$content: Content object to be previewed (may be replaced by hook function)

'EditPageNoSuchSection': When a section edit request is given for an
non-existent section
&$editpage: The current EditPage object
&$res: the HTML of the error text

'EditPageTosSummary': Give a chance for site and per-namespace customizations
of terms of service summary link that might exist separately from the copyright
notice.
$title: title of page being edited
&$msg: localization message name, overridable. Default is 'editpage-tos-summary'

'EmailConfirmed': When checking that the user's email address is "confirmed".
This runs before the other checks, such as anonymity and the real check; return
true to allow those checks to occur, and false if checking is done.
&$user: User being checked
&$confirmed: Whether or not the email address is confirmed

'EmailUser': Before sending email from one user to another.
&$to: MailAddress object of receiving user
&$from: MailAddress object of sending user
&$subject: subject of the mail
&$text: text of the mail
&$error: Out-param for an error. Should be set to a Status object or boolean
  false.

'EmailUserCC': Before sending the copy of the email to the author.
&$to: MailAddress object of receiving user
&$from: MailAddress object of sending user
&$subject: subject of the mail
&$text: text of the mail

'EmailUserComplete': After sending email from one user to another.
$to: MailAddress object of receiving user
$from: MailAddress object of sending user
$subject: subject of the mail
$text: text of the mail

'EmailUserForm': After building the email user form object.
&$form: HTMLForm object

'EmailUserPermissionsErrors': to retrieve permissions errors for emailing a
user.
$user: The user who is trying to email another user.
$editToken: The user's edit token.
&$hookErr: Out-param for the error. Passed as the parameters to
  OutputPage::showErrorPage.

'EnhancedChangesList::getLogText': to alter, remove or add to the links of a
group of changes in EnhancedChangesList.
Hook subscribers can return false to omit this line from recentchanges.
$changesList: EnhancedChangesList object
&$links: The links that were generated by EnhancedChangesList
$block: The RecentChanges objects in that block

'EnhancedChangesListModifyLineData': to alter data used to build
a grouped recent change inner line in EnhancedChangesList.
Hook subscribers can return false to omit this line from recentchanges.
$changesList: EnhancedChangesList object
&$data: An array with all the components that will be joined in order to create
  the line
$block: An array of RecentChange objects in that block
$rc: The RecentChange object for this line
&$classes: An array of classes to change
&$attribs: associative array of other HTML attributes for the <tr> element.
  Currently only data attributes reserved to MediaWiki are allowed
  (see Sanitizer::isReservedDataAttribute).

'EnhancedChangesListModifyBlockLineData': to alter data used to build
a non-grouped recent change line in EnhancedChangesList.
$changesList: EnhancedChangesList object
&$data: An array with all the components that will be joined in order to create
  the line
$rc: The RecentChange object for this line

'ExemptFromAccountCreationThrottle': Exemption from the account creation
throttle.
$ip: The ip address of the user

'ExtensionTypes': Called when generating the extensions credits, use this to
change the tables headers.
&$extTypes: associative array of extensions types

'FetchChangesList': When fetching the ChangesList derivative for a particular
user.
$user: User the list is being fetched for
&$skin: Skin object to be used with the list
&$list: List object (defaults to NULL, change it to an object instance and
  return false override the list derivative used)

'FileDeleteComplete': When a file is deleted.
&$file: reference to the deleted file
&$oldimage: in case of the deletion of an old image, the name of the old file
&$article: in case all revisions of the file are deleted a reference to the
  WikiFilePage associated with the file.
&$user: user who performed the deletion
&$reason: reason

'FileTransformed': When a file is transformed and moved into storage.
$file: reference to the File object
$thumb: the MediaTransformOutput object
$tmpThumbPath: The temporary file system path of the transformed file
$thumbPath: The permanent storage path of the transformed file

'FileUndeleteComplete': When a file is undeleted
$title: title object to the file
$fileVersions: array of undeleted versions. Empty if all versions were restored
$user: user who performed the undeletion
$reason: reason

'FileUpload': When a file upload occurs.
$file: Image object representing the file that was uploaded
$reupload: Boolean indicating if there was a previously another image there or
  not (since 1.17)
$hasDescription: Boolean indicating that there was already a description page
  and a new one from the comment wasn't created (since 1.17)

'FormatAutocomments': When an autocomment is formatted by the Linker.
&$comment: Reference to the accumulated comment. Initially null, when set the
  default code will be skipped.
$pre: Boolean, true if there is text before this autocomment
$auto: The extracted part of the parsed comment before the call to the hook.
$post: Boolean, true if there is text after this autocomment
$title: An optional title object used to links to sections. Can be null.
$local: Boolean indicating whether section links should refer to local page.
$wikiId: String containing the ID (as used by WikiMap) of the wiki from which the
  autocomment originated; null for the local wiki. Added in 1.26, should default
  to null in handler functions, for backwards compatibility.

'GalleryGetModes': Get list of classes that can render different modes of a
gallery.
&$modeArray: An associative array mapping mode names to classes that implement
  that mode. It is expected all registered classes are a subclass of
  ImageGalleryBase.

'GetAutoPromoteGroups': When determining which autopromote groups a user is
entitled to be in.
$user: user to promote.
&$promote: groups that will be added.

'GetBlockedStatus': after loading blocking status of an user from the database
&$user: user (object) being checked

'GetCacheVaryCookies': Get cookies that should vary cache options.
$out: OutputPage object
&$cookies: array of cookies name, add a value to it if you want to add a cookie
  that have to vary cache options

'GetCanonicalURL': Modify fully-qualified URLs used for IRC and e-mail
notifications.
&$title: Title object of page
&$url: string value as output (out parameter, can modify)
$query: query options passed to Title::getCanonicalURL()

'GetContentModels': Add content models to the list of available models.
&$models: array containing current model list, as strings. Extensions should add to this list.

'GetDefaultSortkey': Override the default sortkey for a page.
$title: Title object that we need to get a sortkey for
&$sortkey: Sortkey to use.

'GetDifferenceEngine': Called when getting a new difference engine interface
object Return false for valid object in $differenceEngine or true for the
default difference engine.
$context: IContextSource context to be used for diff
$old: Revision ID to show and diff with
$new: Either a revision ID or one of the strings 'cur', 'prev' or 'next'
$refreshCache: If set, refreshes the diff cache
$unhide: If set, allow viewing deleted revs
&$differenceEngine: output parameter, difference engine object to be used for
  diff

'GetDoubleUnderscoreIDs': Modify the list of behavior switch (double
underscore) magic words. Called by MagicWord.
&$doubleUnderscoreIDs: array of strings

'GetExtendedMetadata': Get extended file metadata for the API
&$combinedMeta: Array of the form:
        'MetadataPropName' => [
                value' => prop value,
                'source' => 'name of hook'
         ].
$file: File object of file in question
$context: RequestContext (including language to use)
$single: Only extract the current language; if false, the prop value should
  be in the metadata multi-language array format:
  mediawiki.org/wiki/Manual:File_metadata_handling#Multi-language_array_format
&$maxCacheTime: how long the results can be cached

'GetFullURL': Modify fully-qualified URLs used in redirects/export/offsite data.
&$title: Title object of page
&$url: string value as output (out parameter, can modify)
$query: query options passed to Title::getFullURL()

'GetHumanTimestamp': Pre-emptively override the human-readable timestamp
generated by MWTimestamp::getHumanTimestamp(). Return false in this hook to use
the custom output.
&$output: string for the output timestamp
$timestamp: MWTimestamp object of the current (user-adjusted) timestamp
$relativeTo: MWTimestamp object of the relative (user-adjusted) timestamp
$user: User whose preferences are being used to make timestamp
$lang: Language that will be used to render the timestamp

'GetInternalURL': Modify fully-qualified URLs used for squid cache purging.
&$title: Title object of page
&$url: string value as output (out parameter, can modify)
$query: query options passed to Title::getInternalURL()

'GetIP': modify the ip of the current user (called only once).
&$ip: string holding the ip as determined so far

'GetLangPreferredVariant': Called in LanguageConverter#getPreferredVariant() to
  allow fetching the language variant code from cookies or other such
  alternative storage.
&$req: language variant from the URL (string) or boolean false if no variant
  was specified in the URL; the value of this variable comes from
  LanguageConverter#getURLVariant()

'GetLinkColours': modify the CSS class of an array of page links.
$linkcolour_ids: array of prefixed DB keys of the pages linked to,
  indexed by page_id.
&$colours: (output) array of CSS classes, indexed by prefixed DB keys

'GetLocalURL': Modify local URLs as output into page links. Note that if you are
working with internal urls (non-interwiki) then it may be preferable to work
with the GetLocalURL::Internal or GetLocalURL::Article hooks as GetLocalURL can
be buggy for internal urls on render if you do not re-implement the horrible
hack that Title::getLocalURL uses in your own extension.
&$title: Title object of page
&$url: string value as output (out parameter, can modify)
$query: query options passed to Title::getLocalURL()

'GetLocalURL::Article': Modify local URLs specifically pointing to article paths
without any fancy queries or variants.
&$title: Title object of page
&$url: string value as output (out parameter, can modify)

'GetLocalURL::Internal': Modify local URLs to internal pages.
&$title: Title object of page
&$url: string value as output (out parameter, can modify)
$query: query options passed to Title::getLocalURL()

'GetLogTypesOnUser': Add log types where the target is a userpage
&$types: Array of log types

'GetMetadataVersion': Modify the image metadata version currently in use. This
is used when requesting image metadata from a ForeignApiRepo. Media handlers
that need to have versioned metadata should add an element to the end of the
version array of the form 'handler_name=version'. Most media handlers won't need
to do this unless they broke backwards compatibility with a previous version of
the media handler metadata output.
&$version: Array of version strings

'GetNewMessagesAlert': Disable or modify the new messages alert
&$newMessagesAlert: An empty string by default. If the user has new talk page
  messages, this should be populated with an alert message to that effect
$newtalks: An empty array if the user has no new messages or an array
  containing links and revisions if there are new messages (See
  User::getNewMessageLinks)
$user: The user object of the user who is loading the page
$out: OutputPage object (to check what type of page the user is on)

'GetPreferences': Modify user preferences.
$user: User whose preferences are being modified.
&$preferences: Preferences description array, to be fed to an HTMLForm object

'GetRelativeTimestamp': Pre-emptively override the relative timestamp generated
by MWTimestamp::getRelativeTimestamp(). Return false in this hook to use the
custom output.
&$output: string for the output timestamp
&$diff: DateInterval representing the difference between the timestamps
$timestamp: MWTimestamp object of the current (user-adjusted) timestamp
$relativeTo: MWTimestamp object of the relative (user-adjusted) timestamp
$user: User whose preferences are being used to make timestamp
$lang: Language that will be used to render the timestamp

'getUserPermissionsErrors': Add a permissions error when permissions errors are
checked for. Use instead of userCan for most cases. Return false if the user
can't do it, and populate $result with the reason in the form of
[ messagename, param1, param2, ... ] or a MessageSpecifier instance (you
might want to use ApiMessage to provide machine-readable details for the API).
For consistency, error messages
should be plain text with no special coloring, bolding, etc. to show that
they're errors; presenting them properly to the user as errors is done by the
caller.
&$title: Title object being checked against
&$user: Current user object
$action: Action being checked
&$result: User permissions error to add. If none, return true.

'getUserPermissionsErrorsExpensive': Equal to getUserPermissionsErrors, but is
called only if expensive checks are enabled. Add a permissions error when
permissions errors are checked for. Return false if the user can't do it, and
populate $result with the reason in the form of [ messagename, param1, param2,
... ] or a MessageSpecifier instance (you might want to use ApiMessage to
provide machine-readable details for the API). For consistency, error messages
should be plain text with no special coloring, bolding, etc. to show that
they're errors; presenting them properly to the user as errors is done by the
caller.
&$title: Title object being checked against
&$user: Current user object
$action: Action being checked
&$result: User permissions error to add. If none, return true.

'GitViewers': Called when generating the list of git viewers for
Special:Version, use this to change the list.
&$extTypes: associative array of repo URLS to viewer URLs.

'HistoryRevisionTools': Override or extend the revision tools available from the
page history view, i.e. undo, rollback, etc.
$rev: Revision object
&$links: Array of HTML links
$prevRev: Revision object, next in line in page history, or null
$user: Current user object

'HTMLFileCache::useFileCache': Override whether a page should be cached in file
cache.
$context: An IContextSource object with information about the request being
  served.

'ImageBeforeProduceHTML': Called before producing the HTML created by a wiki
image insertion. You can skip the default logic entirely by returning false, or
just modify a few things using call-by-reference.
&$skin: Skin object
&$title: Title object of the image
&$file: File object, or false if it doesn't exist
&$frameParams: Various parameters with special meanings; see documentation in
  includes/Linker.php for Linker::makeImageLink
&$handlerParams: Various parameters with special meanings; see documentation in
  includes/Linker.php for Linker::makeImageLink
&$time: Timestamp of file in 'YYYYMMDDHHIISS' string form, or false for current
&$res: Final HTML output, used if you return false
$parser: Parser instance
&$query: Query params for desc URL
&$widthOption: Used by the parser to remember the user preference thumbnailsize

'ImageOpenShowImageInlineBefore': Call potential extension just before showing
the image on an image page.
&$imagePage: ImagePage object ($this)
&$output: $wgOut

'ImagePageAfterImageLinks': Called after the image links section on an image
page is built.
$imagePage: ImagePage object ($this)
&$html: HTML for the hook to add

'ImagePageFileHistoryLine': Called when a file history line is constructed.
$imagePage: ImagePage object ($this)
$file: the file
&$line: the HTML of the history line
&$css: the line CSS class

'ImagePageFindFile': Called when fetching the file associated with an image
page.
$page: ImagePage object
&$file: File object
&$displayFile: displayed File object

'ImagePageShowTOC': Called when the file toc on an image page is generated.
$page: ImagePage object
&$toc: Array of <li> strings

'ImgAuthBeforeStream': executed before file is streamed to user, but only when
using img_auth.php.
&$title: the Title object of the file as it would appear for the upload page
&$path: the original file and path name when img_auth was invoked by the web
  server
&$name: the name only component of the file
&$result: The location to pass back results of the hook routine (only used if
  failed)
  $result[0]=The index of the header message
  $result[1]=The index of the body text message
  $result[2 through n]=Parameters passed to body text message. Please note the
  header message cannot receive/use parameters.

'ImportHandleLogItemXMLTag': When parsing a XML tag in a log item.
Return false to stop further processing of the tag
$reader: XMLReader object
$logInfo: Array of information

'ImportHandlePageXMLTag': When parsing a XML tag in a page.
Return false to stop further processing of the tag
$reader: XMLReader object
&$pageInfo: Array of information

'ImportHandleRevisionXMLTag': When parsing a XML tag in a page revision.
Return false to stop further processing of the tag
$reader: XMLReader object
$pageInfo: Array of page information
$revisionInfo: Array of revision information

'ImportHandleToplevelXMLTag': When parsing a top level XML tag.
Return false to stop further processing of the tag
$reader: XMLReader object

'ImportHandleUnknownUser': When a user doesn't exist locally, this hook is
called to give extensions an opportunity to auto-create it. If the auto-creation
is successful, return false.
$name: User name

'ImportHandleUploadXMLTag': When parsing a XML tag in a file upload.
Return false to stop further processing of the tag
$reader: XMLReader object
$revisionInfo: Array of information

'ImportLogInterwikiLink': Hook to change the interwiki link used in log entries
and edit summaries for transwiki imports.
&$fullInterwikiPrefix: Interwiki prefix, may contain colons.
&$pageTitle: String that contains page title.

'ImportSources': Called when reading from the $wgImportSources configuration
variable. Can be used to lazy-load the import sources list.
&$importSources: The value of $wgImportSources. Modify as necessary. See the
comment in DefaultSettings.php for the detail of how to structure this array.

'InfoAction': When building information to display on the action=info page.
$context: IContextSource object
&$pageInfo: Array of information

'InitializeArticleMaybeRedirect': MediaWiki check to see if title is a redirect.
&$title: Title object for the current page
&$request: WebRequest
&$ignoreRedirect: boolean to skip redirect check
&$target: Title/string of redirect target
&$article: Article object

'InternalParseBeforeLinks': during Parser's internalParse method before links
but after nowiki/noinclude/includeonly/onlyinclude and other processings.
&$parser: Parser object
&$text: string containing partially parsed text
&$stripState: Parser's internal StripState object

'InternalParseBeforeSanitize': during Parser's internalParse method just before
the parser removes unwanted/dangerous HTML tags and after nowiki/noinclude/
includeonly/onlyinclude and other processings. Ideal for syntax-extensions after
template/parser function execution which respect nowiki and HTML-comments.
&$parser: Parser object
&$text: string containing partially parsed text
&$stripState: Parser's internal StripState object

'InterwikiLoadPrefix': When resolving if a given prefix is an interwiki or not.
Return true without providing an interwiki to continue interwiki search.
$prefix: interwiki prefix we are looking for.
&$iwData: output array describing the interwiki with keys iw_url, iw_local,
  iw_trans and optionally iw_api and iw_wikiid.

'InvalidateEmailComplete': Called after a user's email has been invalidated
successfully.
$user: user (object) whose email is being invalidated

'IRCLineURL': When constructing the URL to use in an IRC notification.
Callee may modify $url and $query, URL will be constructed as $url . $query
&$url: URL to index.php
&$query: Query string
$rc: RecentChange object that triggered url generation

'IsFileCacheable': Override the result of Article::isFileCacheable() (if true)
&$article: article (object) being checked

'IsTrustedProxy': Override the result of IP::isTrustedProxy()
&$ip: IP being check
&$result: Change this value to override the result of IP::isTrustedProxy()

'IsUploadAllowedFromUrl': Override the result of UploadFromUrl::isAllowedUrl()
$url: URL used to upload from
&$allowed: Boolean indicating if uploading is allowed for given URL

'isValidEmailAddr': Override the result of Sanitizer::validateEmail(), for
instance to return false if the domain name doesn't match your organization.
$addr: The e-mail address entered by the user
&$result: Set this and return false to override the internal checks

'isValidPassword': Override the result of User::isValidPassword()
$password: The password entered by the user
&$result: Set this and return false to override the internal checks
$user: User the password is being validated for

'Language::getMessagesFileName':
$code: The language code or the language we're looking for a messages file for
&$file: The messages file path, you can override this to change the location.

'LanguageGetMagic': DEPRECATED since 1.16! Use $magicWords in a file listed in
$wgExtensionMessagesFiles instead.
Use this to define synonyms of magic words depending of the language
&$magicExtensions: associative array of magic words synonyms
$lang: language code (string)

'LanguageGetNamespaces': Provide custom ordering for namespaces or
remove namespaces. Do not use this hook to add namespaces. Use
CanonicalNamespaces for that.
&$namespaces: Array of namespaces indexed by their numbers

'LanguageGetSpecialPageAliases': DEPRECATED! Use $specialPageAliases in a file
listed in $wgExtensionMessagesFiles instead.
Use to define aliases of special pages names depending of the language
&$specialPageAliases: associative array of magic words synonyms
$lang: language code (string)

'LanguageGetTranslatedLanguageNames': Provide translated language names.
&$names: array of language code => language name
$code: language of the preferred translations

'LanguageLinks': Manipulate a page's language links. This is called
in various places to allow extensions to define the effective language
links for a page.
$title: The page's Title.
&$links: Array with elements of the form "language:title" in the order
  that they will be output.
&$linkFlags: Associative array mapping prefixed links to arrays of flags.
  Currently unused, but planned to provide support for marking individual
  language links in the UI, e.g. for featured articles.

'LanguageSelector': Hook to change the language selector available on a page.
$out: The output page.
$cssClassName: CSS class name of the language selector.

'LinkBegin': DEPRECATED since 1.28! Use HtmlPageLinkRendererBegin instead.
Used when generating internal and interwiki links in Linker::link(), before
processing starts.  Return false to skip default processing and return $ret. See
documentation for Linker::link() for details on the expected meanings of
parameters.
$skin: the Skin object
$target: the Title that the link is pointing to
&$html: the contents that the <a> tag should have (raw HTML); null means
  "default".
&$customAttribs: the HTML attributes that the <a> tag should have, in
  associative array form, with keys and values unescaped.  Should be merged
  with default values, with a value of false meaning to suppress the
  attribute.
&$query: the query string to add to the generated URL (the bit after the "?"),
  in associative array form, with keys and values unescaped.
&$options: array of options.  Can include 'known', 'broken', 'noclasses'.
&$ret: the value to return if your hook returns false.

'LinkEnd': DEPRECATED since 1.28! Use HtmlPageLinkRendererEnd hook instead
Used when generating internal and interwiki links in Linker::link(),
just before the function returns a value.  If you return true, an <a> element
with HTML attributes $attribs and contents $html will be returned.  If you
return false, $ret will be returned.
$skin: the Skin object
$target: the Title object that the link is pointing to
$options: the options.  Will always include either 'known' or 'broken', and may
  include 'noclasses'.
&$html: the final (raw HTML) contents of the <a> tag, after processing.
&$attribs: the final HTML attributes of the <a> tag, after processing, in
  associative array form.
&$ret: the value to return if your hook returns false.

'LinkerMakeExternalImage': At the end of Linker::makeExternalImage() just
before the return.
&$url: the image url
&$alt: the image's alt text
&$img: the new image HTML (if returning false)

'LinkerMakeExternalLink': At the end of Linker::makeExternalLink() just
before the return.
&$url: the link url
&$text: the link text
&$link: the new link HTML (if returning false)
&$attribs: the attributes to be applied.
$linkType: The external link type

'LinkerMakeMediaLinkFile': At the end of Linker::makeMediaLinkFile() just
before the return.
$title: the Title object that the link is pointing to
$file: the File object or false if broken link
&$html: the link text
&$attribs: the attributes to be applied
&$ret: the value to return if your hook returns false

'LogEventsListLineEnding': Called before a Special:Log line is finished
$page: the LogEventsList object
&$ret: the HTML line
$entry: the DatabaseLogEntry object for this row
&$classes: the classes to add to the surrounding <li>
&$attribs: associative array of other HTML attributes for the <li> element.
  Currently only data attributes reserved to MediaWiki are allowed
  (see Sanitizer::isReservedDataAttribute).


'HtmlPageLinkRendererBegin':
Used when generating internal and interwiki links in
LinkRenderer, before processing starts.  Return false to skip default
processing and return $ret.
$linkRenderer: the LinkRenderer object
$target: the LinkTarget that the link is pointing to
&$text: the contents that the <a> tag should have; either a plain, unescaped
  string or a HtmlArmor object; null means "default".
&$customAttribs: the HTML attributes that the <a> tag should have, in
  associative array form, with keys and values unescaped.  Should be merged
  with default values, with a value of false meaning to suppress the
  attribute.
&$query: the query string to add to the generated URL (the bit after the "?"),
  in associative array form, with keys and values unescaped.
&$ret: the value to return if your hook returns false.

'HtmlPageLinkRendererEnd':
Used when generating internal and interwiki links in LinkRenderer,
just before the function returns a value.  If you return true, an <a> element
with HTML attributes $attribs and contents $html will be returned.  If you
return false, $ret will be returned.
$linkRenderer: the LinkRenderer object
$target: the LinkTarget object that the link is pointing to
$isKnown: boolean indicating whether the page is known or not
&$text: the contents that the <a> tag should have; either a plain, unescaped
  string or a HtmlArmor object.
&$attribs: the final HTML attributes of the <a> tag, after processing, in
  associative array form.
&$ret: the value to return if your hook returns false.

'LinksUpdate': At the beginning of LinksUpdate::doUpdate() just before the
actual update.
&$linksUpdate: the LinksUpdate object

'LinksUpdateAfterInsert': At the end of LinksUpdate::incrTableUpdate() after
each link table insert.  For example, pagelinks, imagelinks, externallinks.
$linksUpdate: LinksUpdate object
$table: the table to insert links to
$insertions: an array of links to insert

'LinksUpdateComplete': At the end of LinksUpdate::doUpdate() when updating,
including delete and insert, has completed for all link tables
&$linksUpdate: the LinksUpdate object
$ticket: prior result of LBFactory::getEmptyTransactionTicket()

'LinksUpdateConstructed': At the end of LinksUpdate() is construction.
&$linksUpdate: the LinksUpdate object

'ListDefinedTags': When trying to find all defined tags.
&$tags: The list of tags.

'LoadExtensionSchemaUpdates': Called during database installation and updates.
$updater: A DatabaseUpdater subclass

'LocalFile::getHistory': Called before file history query performed.
&$file: the File object
&$tables: tables
&$fields: select fields
&$conds: conditions
&$opts: query options
&$join_conds: JOIN conditions

'LocalFilePurgeThumbnails': Called before thumbnails for a local file a purged.
$file: the File object
$archiveName: name of an old file version or false if it's the current one

'LocalisationCacheRecache': Called when loading the localisation data into
cache.
$cache: The LocalisationCache object
$code: language code
&$alldata: The localisation data from core and extensions
&$purgeBlobs: whether to purge/update the message blobs via
  MessageBlobStore::clear()

'LocalisationCacheRecacheFallback': Called for each language when merging
fallback data into the cache.
$cache: The LocalisationCache object
$code: language code
&$alldata: The localisation data from core and extensions. Note some keys may
  be omitted if they won't be merged into the final result.

'LocalisationChecksBlacklist': When fetching the blacklist of
localisation checks.
&$blacklist: array of checks to blacklist. See the bottom of
  maintenance/language/checkLanguage.inc for the format of this variable.

'LocalisationIgnoredOptionalMessages': When fetching the list of ignored and
optional localisation messages
&$ignored: Array of ignored message keys
&$optional: Array of optional message keys

'LocalUserCreated': Called when a local user has been created
$user: User object for the created user
$autocreated: Boolean, whether this was an auto-creation

'LogEventsListGetExtraInputs': When getting extra inputs to display on
Special:Log for a specific log type
$type: String of log type being displayed
$logEventsList: LogEventsList object for context and access to the WebRequest
&$input: string HTML of an input element

'LogEventsListShowLogExtract': Called before the string is added to OutputPage.
Returning false will prevent the string from being added to the OutputPage.
&$s: html string to show for the log extract
$types: String or Array Log types to show
$page: String or Title The page title to show log entries for
$user: String The user who made the log entries
$param: Associative Array with the following additional options:
  - lim Integer Limit of items to show, default is 50
  - conds Array Extra conditions for the query (e.g. "log_action != 'revision'")
  - showIfEmpty boolean Set to false if you don't want any output in case the
    loglist is empty if set to true (default), "No matching items in log" is
    displayed if loglist is empty
  - msgKey Array If you want a nice box with a message, set this to the key of
    the message. First element is the message key, additional optional elements
    are parameters for the key that are processed with
    wfMessage()->params()->parseAsBlock()
  - offset Set to overwrite offset parameter in $wgRequest set to '' to unset
    offset
  - wrap String Wrap the message in html (usually something like
    "&lt;div ...>$1&lt;/div>").
  - flags Integer display flags (NO_ACTION_LINK,NO_EXTRA_USER_LINKS)

'LogException': Called before an exception (or PHP error) is logged. This is
meant for integration with external error aggregation services; returning false
will NOT prevent logging.
$e: The exception (in case of a plain old PHP error, a wrapping ErrorException)
$suppressed: true if the error was suppressed via
  error_reporting()/wfSuppressWarnings()

'LoginFormValidErrorMessages': Called in LoginForm when a function gets valid
error messages. Allows to add additional error messages (except messages already
in LoginForm::$validErrorMessages).
&$messages: Already added messages (inclusive messages from
  LoginForm::$validErrorMessages)

'LoginUserMigrated': DEPRECATED since 1.27! Create a PreAuthenticationProvider
instead. Called during login to allow extensions the opportunity to inform a
user that their username doesn't exist for a specific reason, instead of letting
the login form give the generic error message that the account does not exist.
For example, when the account has been renamed or deleted.
$user: the User object being authenticated against.
&$msg: the message identifier for abort reason, or an array to pass a message
  key and parameters.

'LogLine': Processes a single log entry on Special:Log.
$log_type: string for the type of log entry (e.g. 'move'). Corresponds to
  logging.log_type database field.
$log_action: string for the type of log action (e.g. 'delete', 'block',
  'create2'). Corresponds to logging.log_action database field.
$title: Title object that corresponds to logging.log_namespace and
  logging.log_title database fields.
$paramArray: Array of parameters that corresponds to logging.log_params field.
  Note that only $paramArray[0] appears to contain anything.
&$comment: string that corresponds to logging.log_comment database field, and
  which is displayed in the UI.
&$revert: string that is displayed in the UI, similar to $comment.
$time: timestamp of the log entry (added in 1.12)

'LonelyPagesQuery': Allow extensions to modify the query used by
Special:LonelyPages.
&$tables: tables to join in the query
&$conds: conditions for the query
&$joinConds: join conditions for the query

'MagicWordwgVariableIDs': When defining new magic words IDs.
&$variableIDs: array of strings

'MaintenanceRefreshLinksInit': before executing the refreshLinks.php maintenance
script.
$refreshLinks: RefreshLinks object

'MakeGlobalVariablesScript': Called at end of OutputPage::getJSVars.
Ideally, this hook should only be used to add variables that depend on
the current page/request; static configuration should be added through
ResourceLoaderGetConfigVars instead.
&$vars: variable (or multiple variables) to be added into the output of
  Skin::makeVariablesScript
$out: The OutputPage which called the hook, can be used to get the real title.

'MarkPatrolled': Before an edit is marked patrolled.
$rcid: ID of the revision to be marked patrolled
&$user: the user (object) marking the revision as patrolled
$wcOnlySysopsCanPatrol: config setting indicating whether the user needs to be a
  sysop in order to mark an edit patrolled.
$auto: true if the edit is being marked as patrolled automatically

'MarkPatrolledComplete': After an edit is marked patrolled.
$rcid: ID of the revision marked as patrolled
&$user: user (object) who marked the edit patrolled
$wcOnlySysopsCanPatrol: config setting indicating whether the user must be a
  sysop to patrol the edit.
$auto: true if the edit is being marked as patrolled automatically

'ApiMaxLagInfo': When lag information is being requested via API. Use this to
override lag information. Generally a hook function should only replace
$lagInfo if the new $lagInfo['lag'] is greater than the current $lagInfo['lag'].
&$lagInfo: Maximum lag information array. Fields in the array are:
  'lag' is the number of seconds of lag.
  'host' is the host name on which the lag exists.
  'type' is an indication of the type of lag,
    e.g. "db" for database replication lag or "jobqueue" for job queue size
    converted to pseudo-seconds.
  It is possible to add more fields and they will be returned to the user in
  the API response.

'MediaWikiPerformAction': Override MediaWiki::performAction(). Use this to do
something completely different, after the basic globals have been set up, but
before ordinary actions take place.
$output: $wgOut
$article: Article on which the action will be performed
$title: Title on which the action will be performed
$user: $wgUser
$request: $wgRequest
$mediaWiki: The $mediawiki object

'MediaWikiServices': Called when a global MediaWikiServices instance is
initialized. Extensions may use this to define, replace, or wrap services.
However, the preferred way to define a new service is
the $wgServiceWiringFiles array.
$services: MediaWikiServices

'MessageCache::get': When fetching a message. Can be used to override the key
for customisations. Given and returned message key must be in special format:
1) first letter must be in lower case according to the content language.
2) spaces must be replaced with underscores
&$key: message key (string)

'MessageCacheReplace': When a message page is changed. Useful for updating
caches.
$title: name of the page changed.
$text: new contents of the page.

'MessagesPreLoad': When loading a message from the database.
$title: title of the message (string)
&$message: value (string), change it to the message you want to define
$code: code (string) denoting the language to try.

'MimeMagicGuessFromContent': Allows MW extensions guess the MIME by content.
$mimeMagic: Instance of MimeMagic.
&$head: First 1024 bytes of the file in a string (in - Do not alter!).
&$tail: More or equal than last 65558 bytes of the file in a string
  (in - Do not alter!).
$file: File path.
&$mime: MIME type (out).

'MimeMagicImproveFromExtension': Allows MW extensions to further improve the
MIME type detected by considering the file extension.
$mimeMagic: Instance of MimeMagic.
$ext: File extension.
&$mime: MIME type (in/out).

'MimeMagicInit': Before processing the list mapping MIME types to media types
and the list mapping MIME types to file extensions.
As an extension author, you are encouraged to submit patches to MediaWiki's
core to add new MIME types to mime.types.
$mimeMagic: Instance of MimeMagic.
  Use $mimeMagic->addExtraInfo( $stringOfInfo );
  for adding new MIME info to the list.
  Use $mimeMagic->addExtraTypes( $stringOfTypes );
  for adding new MIME types to the list.

'ModifyExportQuery': Modify the query used by the exporter.
$db: The database object to be queried.
&$tables: Tables in the query.
&$conds: Conditions in the query.
&$opts: Options for the query.
&$join_conds: Join conditions for the query.

'MovePageCheckPermissions': Specify whether the user is allowed to move the
page.
$oldTitle: Title object of the current (old) location
$newTitle: Title object of the new location
$user: User making the move
$reason: string of the reason provided by the user
$status: Status object to pass error messages to

'MovePageIsValidMove': Specify whether a page can be moved for technical
reasons.
$oldTitle: Title object of the current (old) location
$newTitle: Title object of the new location
$status: Status object to pass error messages to

'NamespaceIsMovable': Called when determining if it is possible to pages in a
namespace.
$index: Integer; the index of the namespace being checked.
&$result: Boolean; whether MediaWiki currently thinks that pages in this
  namespace are movable. Hooks may change this value to override the return
  value of MWNamespace::isMovable().

'NewDifferenceEngine': Called when a new DifferenceEngine object is made
$title: the diff page title (nullable)
&$oldId: the actual old Id to use in the diff
&$newId: the actual new Id to use in the diff (0 means current)
$old: the ?old= param value from the url
$new: the ?new= param value from the url

'NewPagesLineEnding': Called before a NewPages line is finished.
$page: the SpecialNewPages object
&$ret: the HTML line
$row: the database row for this page (the recentchanges record and a few extras
  - see NewPagesPager::getQueryInfo)
&$classes: the classes to add to the surrounding <li>
&$attribs: associative array of other HTML attributes for the <li> element.
  Currently only data attributes reserved to MediaWiki are allowed
  (see Sanitizer::isReservedDataAttribute).

'NewRevisionFromEditComplete': Called when a revision was inserted due to an
edit.
$wikiPage: the WikiPage edited
$rev: the new revision
$baseID: the revision ID this was based off, if any
$user: the editing user
&$tags: tags to apply to the edit and recent change

'OldChangesListRecentChangesLine': Customize entire recent changes line, or
return false to omit the line from RecentChanges and Watchlist special pages.
&$changeslist: The OldChangesList instance.
&$s: HTML of the form "<li>...</li>" containing one RC entry.
$rc: The RecentChange object.
&$classes: array of css classes for the <li> element.
&$attribs: associative array of other HTML attributes for the <li> element.
  Currently only data attributes reserved to MediaWiki are allowed
  (see Sanitizer::isReservedDataAttribute).

'OpenSearchUrls': Called when constructing the OpenSearch description XML. Hooks
can alter or append to the array of URLs for search & suggestion formats.
&$urls: array of associative arrays with Url element attributes

'OpportunisticLinksUpdate': Called by WikiPage::triggerOpportunisticLinksUpdate
when a page view triggers a re-rendering of the page. This may happen
particularly if the parser cache is split by user language, and no cached
rendering of the page exists in the user's language. The hook is called
before checking whether page_links_updated indicates that the links are up
to date. Returning false will cause triggerOpportunisticLinksUpdate() to abort
without triggering any updates.
$page: the Page that was rendered.
$title: the Title of the rendered page.
$parserOutput: ParserOutput resulting from rendering the page.

'OtherAutoblockLogLink': Get links to the autoblock log from extensions which
autoblocks users and/or IP addresses too.
&$otherBlockLink: An array with links to other autoblock logs

'OtherBlockLogLink': Get links to the block log from extensions which blocks
users and/or IP addresses too.
&$otherBlockLink: An array with links to other block logs
$ip: The requested IP address or username

'OutputPageBeforeHTML': A page has been processed by the parser and the
resulting HTML is about to be displayed.
&$parserOutput: the parserOutput (object) that corresponds to the page
&$text: the text that will be displayed, in HTML (string)

'OutputPageBodyAttributes': Called when OutputPage::headElement is creating the
body tag to allow for extensions to add attributes to the body of the page they
might need. Or to allow building extensions to add body classes that aren't of
high enough demand to be included in core.
$out: The OutputPage which called the hook, can be used to get the real title
$sk: The Skin that called OutputPage::headElement
&$bodyAttrs: An array of attributes for the body tag passed to Html::openElement

'OutputPageCheckLastModified': when checking if the page has been modified
since the last visit.
&$modifiedTimes: array of timestamps.
  The following keys are set: page, user, epoch
$out: OutputPage object (since 1.28)

'OutputPageMakeCategoryLinks': Links are about to be generated for the page's
categories. Implementations should return false if they generate the category
links, so the default link generation is skipped.
&$out: OutputPage instance (object)
$categories: associative array, keys are category names, values are category
  types ("normal" or "hidden")
&$links: array, intended to hold the result. Must be an associative array with
  category types as keys and arrays of HTML links as values.

'OutputPageParserOutput': after adding a parserOutput to $wgOut
&$out: OutputPage instance (object)
$parserOutput: parserOutput instance being added in $out

'PageContentInsertComplete': After a new article is created.
$wikiPage: WikiPage created
$user: User creating the article
$content: New content as a Content object
$summary: Edit summary/comment
$isMinor: Whether or not the edit was marked as minor
$isWatch: (No longer used)
$section: (No longer used)
$flags: Flags passed to WikiPage::doEditContent()
$revision: New Revision of the article

'PageContentLanguage': Allows changing the language in which the content of a
page is written. Defaults to the wiki content language ($wgContLang).
$title: Title object
&$pageLang: the page content language (either an object or a language code)
$wgLang: the user language

'PageContentSave': Before an article is saved.
$wikiPage: the WikiPage (object) being saved
$user: the user (object) saving the article
$content: the new article content, as a Content object
$summary: the article summary (comment)
$isminor: minor flag
$iswatch: watch flag
$section: section #

'PageContentSaveComplete': After an article has been updated.
$wikiPage: WikiPage modified
$user: User performing the modification
$content: New content, as a Content object
$summary: Edit summary/comment
$isMinor: Whether or not the edit was marked as minor
$isWatch: (No longer used)
$section: (No longer used)
$flags: Flags passed to WikiPage::doEditContent()
$revision: New Revision of the article (can be null for edits that change
  nothing)
$status: Status object about to be returned by doEditContent()
$baseRevId: the rev ID (or false) this edit was based on
$undidRevId: the rev ID (or 0) this edit undid

'PageHistoryBeforeList': When a history page list is about to be constructed.
&$article: the article that the history is loading for
$context: RequestContext object

'PageHistoryLineEnding': Right before the end <li> is added to a history line.
$historyAction: the action object
&$row: the revision row for this line
&$s: the string representing this parsed line
&$classes: array containing the <li> element classes
&$attribs: associative array of other HTML attributes for the <li> element.
  Currently only data attributes reserved to MediaWiki are allowed
  (see Sanitizer::isReservedDataAttribute).

'PageHistoryPager::doBatchLookups': Called after the pager query was run, before
any output is generated, to allow batch lookups for prefetching information
needed for display. If the hook handler returns false, the regular behavior of
doBatchLookups() is skipped.
$pager: the PageHistoryPager
$result: a ResultWrapper representing the query result

'PageHistoryPager::getQueryInfo': when a history pager query parameter set is
constructed.
&$pager: the pager
&$queryInfo: the query parameters

'PageRenderingHash': NOTE: Consider using ParserOptionsRegister instead.
Alter the parser cache option hash key. A parser extension
which depends on user options should install this hook and append its values to
the key.
&$confstr: reference to a hash key string which can be modified
$user: User (object) requesting the page
&$forOptions: array of options the hash is for

'PageViewUpdates': Allow database (or other) changes to be made after a
page view is seen by MediaWiki.  Note this does not capture views made
via external caches such as Squid.
$wikipage: WikiPage (object) for the page being viewed.
$user: User (object) for the user who is viewing.

'ParserAfterParse': Called from Parser::parse() just after the call to
Parser::internalParse() returns.
&$parser: parser object
&$text: text being parsed
&$stripState: stripState used (object)

'ParserAfterStrip': Called at end of parsing time.
TODO: No more strip, deprecated ?
&$parser: parser object
&$text: text being parsed
&$stripState: stripState used (object)

'ParserAfterTidy': Called after Parser::tidy() in Parser::parse()
&$parser: Parser object being used
&$text: text that will be returned

'ParserAfterUnstrip': Called after the first unstripGeneral() in
Parser::internalParseHalfParsed()
&$parser: Parser object being used
&$text: text that will be returned

'ParserBeforeInternalParse': Called at the beginning of Parser::internalParse().
&$parser: Parser object
&$text: text to parse
&$stripState: StripState instance being used

'ParserBeforeStrip': Called at start of parsing time.
TODO: No more strip, deprecated ?
&$parser: parser object
&$text: text being parsed
&$stripState: stripState used (object)

'ParserBeforeTidy': Called before tidy and custom tags replacements.
&$parser: Parser object being used
&$text: actual text

'ParserCacheSaveComplete': Called after a ParserOutput has been committed to
the parser cache.
$parserCache: ParserCache object $parserOutput was stored in
$parserOutput: ParserOutput object that was stored
$title: Title of the page that was parsed to generate $parserOutput
$popts: ParserOptions used for generating $parserOutput
$revId: ID of the revision that was parsed to create $parserOutput

'ParserClearState': Called at the end of Parser::clearState().
&$parser: Parser object being cleared

'ParserCloned': Called when the parser is cloned.
$parser: Newly-cloned Parser object

'ParserFetchTemplate': Called when the parser fetches a template
$parser: Parser Parser object or false
$title: Title object of the template to be fetched
$rev: Revision object of the template
&$text: Transclusion text of the template or false or null
&$deps: Array of template dependencies with 'title', 'page_id', 'rev_id' keys

'ParserFirstCallInit': Called when the parser initialises for the first time.
&$parser: Parser object being cleared

'ParserGetVariableValueSwitch': Called when the parser need the value of a
custom magic word
&$parser: Parser object
&$varCache: array to store the value in case of multiples calls of the
  same magic word
&$index: index (string) of the magic
&$ret: value of the magic word (the hook should set it)
&$frame: PPFrame object to use for expanding any template variables

'ParserGetVariableValueTs': Use this to change the value of the time for the
{{LOCAL...}} magic word.
&$parser: Parser object
&$time: actual time (timestamp)

'ParserGetVariableValueVarCache': use this to change the value of the variable
cache or return false to not use it.
&$parser: Parser object
&$varCache: variable cache (array)

'ParserLimitReport': DEPRECATED since 1.22! Use ParserLimitReportPrepare and
ParserLimitReportFormat instead.
Called at the end of Parser:parse() when the parser will
include comments about size of the text parsed.
$parser: Parser object
&$limitReport: text that will be included (without comment tags)

'ParserLimitReportFormat': Called for each row in the parser limit report that
needs formatting. If nothing handles this hook, the default is to use "$key" to
get the label, and "$key-value" or "$key-value-text"/"$key-value-html" to
format the value.
$key: Key for the limit report item (string)
&$value: Value of the limit report item
&$report: String onto which to append the data
$isHTML: If true, $report is an HTML table with two columns; if false, it's
  text intended for display in a monospaced font.
$localize: If false, $report should be output in English.

'ParserLimitReportPrepare': Called at the end of Parser:parse() when the parser
will include comments about size of the text parsed. Hooks should use
$output->setLimitReportData() to populate data. Functions for this hook should
not use $wgLang; do that in ParserLimitReportFormat instead.
$parser: Parser object
$output: ParserOutput object

'ParserMakeImageParams': Called before the parser make an image link, use this
to modify the parameters of the image.
$title: title object representing the file
$file: file object that will be used to create the image
&$params: 2-D array of parameters
$parser: Parser object that called the hook

'ParserOptionsRegister': Register additional parser options. Note that if you
change the default value for an option, all existing parser cache entries will
be invalid. To avoid bugs, you'll need to handle that somehow (e.g. with the
RejectParserCacheValue hook) because MediaWiki won't do it for you.
&$defaults: Set the default value for your option here.
&$inCacheKey: To fragment the parser cache on your option, set a truthy value
  here.
&$lazyLoad: To lazy-initialize your option, set it null in $defaults and set a
  callable here. The callable is passed the ParserOptions object and the option
  name.

'ParserOutputPostCacheTransform': Called from ParserOutput::getText() to do
post-cache transforms.
$parserOutput: The ParserOutput object.
&$text: The text being transformed, before core transformations are done.
&$options: The options array being used for the transformation.

'ParserSectionCreate': Called each time the parser creates a document section
from wikitext. Use this to apply per-section modifications to HTML (like
wrapping the section in a DIV).  Caveat: DIVs are valid wikitext, and a DIV
can begin in one section and end in another. Make sure your code can handle
that case gracefully. See the EditSectionClearerLink extension for an example.
$parser: the calling Parser instance
$section: the section number, zero-based, but section 0 is usually empty
&$sectionContent: ref to the content of the section. modify this.
$showEditLinks: boolean describing whether this section has an edit link

'ParserTestGlobals': Allows to define globals for parser tests.
&$globals: Array with all the globals which should be set for parser tests.
  The arrays keys serve as the globals names, its values are the globals values.

'ParserTestTables': Alter the list of tables to duplicate when parser tests are
run. Use when page save hooks require the presence of custom tables to ensure
that tests continue to run properly.
&$tables: array of table names

'ParserOutputStashForEdit': Called when an edit stash parse finishes, before the
output is cached.
$page: the WikiPage of the candidate edit
$content: the Content object of the candidate edit
$output: the ParserOutput result of the candidate edit
$summary: the change summary of the candidate edit
$user: the User considering the edit

'PasswordPoliciesForUser': Alter the effective password policy for a user.
$user: User object whose policy you are modifying
&$effectivePolicy: Array of policy statements that apply to this user

'PerformRetroactiveAutoblock': Called before a retroactive autoblock is applied
to a user.
$block: Block object (which is set to be autoblocking)
&$blockIds: Array of block IDs of the autoblock

'PersonalUrls': Alter the user-specific navigation links (e.g. "my page,
my talk page, my contributions" etc).
&$personal_urls: Array of link specifiers (see SkinTemplate.php)
&$title: Title object representing the current page
$skin: SkinTemplate object providing context (e.g. to check if the user is
  logged in, etc.)

'PingLimiter': Allows extensions to override the results of User::pingLimiter().
&$user: User performing the action
$action: Action being performed
&$result: Whether or not the action should be prevented
  Change $result and return false to give a definitive answer, otherwise
  the built-in rate limiting checks are used, if enabled.
$incrBy: Amount to increment counter by

'PlaceNewSection': Override placement of new sections. Return false and put the
merged text into $text to override the default behavior.
$wikipage: WikiPage object
$oldtext: the text of the article before editing
$subject: subject of the new section
&$text: text of the new section

'PostLoginRedirect': Modify the post login redirect behavior.
Occurs after signing up or logging in, allows for interception of redirect.
&$returnTo: The page name to return to, as a string
&$returnToQuery: array of url parameters, mapping parameter names to values
&$type: type of login redirect as string;
  error: display a return to link ignoring $wgRedirectOnLogin
  signup: display a return to link using $wgRedirectOnLogin if needed
  success: display a return to link using $wgRedirectOnLogin if needed
  successredirect: send an HTTP redirect using $wgRedirectOnLogin if needed

'PreferencesFormPreSave': Override preferences being saved
$formData: array of user submitted data
$form: HTMLForm object, also a ContextSource
$user: User object with preferences to be saved set
&$result: boolean indicating success
$oldUserOptions: array with user old options (before save)

'PreferencesGetLegend': Override the text used for the <legend> of a
preferences section.
$form: the HTMLForm object. This is a ContextSource as well
$key: the section name
&$legend: the legend text. Defaults to wfMessage( "prefs-$key" )->text() but may
  be overridden

'PrefixSearchBackend': DEPRECATED since 1.27! Override
SearchEngine::completionSearchBackend instead.
Override the title prefix search used for OpenSearch and
AJAX search suggestions. Put results into &$results outparam and return false.
$ns: array of int namespace keys to search in
$search: search term (not guaranteed to be conveniently normalized)
$limit: maximum number of results to return
&$results: out param: array of page names (strings)
$offset: number of results to offset from the beginning

'PrefixSearchExtractNamespace': Called if core was not able to extract a
namespace from the search string so that extensions can attempt it.
&$namespaces: array of int namespace keys to search in (change this if you can
  extract namespaces)
&$search: search term (replace this with term without the namespace if you can
  extract one)

'PrefsEmailAudit': Called when user changes their email address.
$user: User (object) changing his email address
$oldaddr: old email address (string)
$newaddr: new email address (string)

'ProtectionForm::buildForm': Called after all protection type fieldsets are made
in the form.
$article: the title being (un)protected
&$output: a string of the form HTML so far

'ProtectionForm::save': Called when a protection form is submitted.
$article: the Page being (un)protected
&$errorMsg: an html message string of an error or an array of message name and
  its parameters
$reasonstr: a string describing the reason page protection level is altered

'ProtectionForm::showLogExtract': Called after the protection log extract is
shown.
$article: the page the form is shown for
$out: OutputPage object

'RandomPageQuery': Lets you modify the query used by Special:Random to select
random pages.
&$tables: Database tables to be used in the query
&$conds: Conditions to be applied in the query
&$joinConds: Join conditions to be applied in the query

'RawPageViewBeforeOutput': Right before the text is blown out in action=raw.
&$obj: RawAction object
&$text: The text that's going to be the output

'RecentChange_save': Called at the end of RecentChange::save().
&$recentChange: RecentChange object

'RecentChangesPurgeRows': Called when old recentchanges rows are purged, after
deleting those rows but within the same transaction.
$rows: The deleted rows as an array of recentchanges row objects (with up to
  $wgUpdateRowsPerQuery items).

'RedirectSpecialArticleRedirectParams': Lets you alter the set of parameter
names such as "oldid" that are preserved when using redirecting special pages
such as Special:MyPage and Special:MyTalk.
&$redirectParams: An array of parameters preserved by redirecting special pages.

'RejectParserCacheValue': Return false to reject an otherwise usable
cached value from the Parser cache. NOTE: CARELESS USE OF THIS HOOK CAN
HAVE CATASTROPHIC CONSEQUENCES FOR HIGH-TRAFFIC INSTALLATIONS. USE WITH
EXTREME CARE.
$parserOutput: ParserOutput value.
$wikiPage: WikiPage object.
$parserOptions: ParserOptions object.

'RequestContextCreateSkin': Called when RequestContext::getSkin creates a skin
instance. Can be used by an extension override what skin is used in certain
contexts.
$context: (IContextSource) The RequestContext the skin is being created for.
&$skin: A variable reference you may set a Skin instance or string key on to
  override the skin that will be used for the context.

'RequestHasSameOriginSecurity': Called to determine if the request is somehow
flagged to lack same-origin security. Return false to indicate the lack. Note
if the "somehow" involves HTTP headers, you'll probably need to make sure
the header is varied on.
$request: The WebRequest object.

'ResetPasswordExpiration': Allow extensions to set a default password expiration
$user: The user having their password expiration reset
&$newExpire: The new expiration date

'ResourceLoaderForeignApiModules': Called from ResourceLoaderForeignApiModule.
Use this to add dependencies to 'mediawiki.ForeignApi' module when you wish
to override its behavior. See the module docs for more information.
&$dependencies: string[] List of modules that 'mediawiki.ForeignApi' should
depend on
$context: ResourceLoaderContext|null

'ResourceLoaderGetConfigVars': Called at the end of
ResourceLoaderStartUpModule::getConfigSettings(). Use this to export static
configuration variables to JavaScript. Things that depend on the current page
or request state must be added through MakeGlobalVariablesScript instead.
&$vars: [ variable name => value ]

'ResourceLoaderJqueryMsgModuleMagicWords': Called in
ResourceLoaderJqueryMsgModule to allow adding magic words for jQueryMsg.
The value should be a string, and they can depend only on the
ResourceLoaderContext.
$context: ResourceLoaderContext
&$magicWords: Associative array mapping all-caps magic word to a string value

'ResourceLoaderRegisterModules': Right before modules information is required,
such as when responding to a resource
loader request or generating HTML output.
&$resourceLoader: ResourceLoader object

'ResourceLoaderTestModules': Let you add new JavaScript testing modules. This is
called after the addition of 'qunit' and MediaWiki testing resources.
&$testModules: array of JavaScript testing modules. The 'qunit' framework,
  included in core, is fed using tests/qunit/QUnitTestResources.php.
  To add a new qunit module named 'myext.tests':
        $testModules['qunit']['myext.tests'] = [
                'script' => 'extension/myext/tests.js',
                'dependencies' => <any module dependency you might have>
         ];
  For QUnit framework, the mediawiki.tests.qunit.testrunner dependency will be
  added to any module.
&$ResourceLoader: object

'RevisionRecordInserted': Called after a revision is inserted into the database.
$revisionRecord: the RevisionRecord that has just been inserted.

'RevisionInsertComplete': DEPRECATED since 1.31! Use RevisionRecordInserted hook
instead. Called after a revision is inserted into the database.
$revision: the Revision
$data: DEPRECATED! Always null!
$flags: DEPRECATED! Always null!

'SearchableNamespaces': An option to modify which namespaces are searchable.
&$arr: Array of namespaces ($nsId => $name) which will be used.

'SearchAfterNoDirectMatch': If there was no match for the exact result. This
runs before lettercase variants are attempted, whereas 'SearchGetNearMatch'
runs after.
$term: Search term string
&$title: Outparam; set to $title object and return false for a match

'SearchGetNearMatch': An extra chance for exact-title-matches in "go" searches
if nothing was found.
$term: Search term string
&$title: Outparam; set to $title object and return false for a match

'SearchGetNearMatchBefore': Perform exact-title-matches in "go" searches before
the normal operations.
$allSearchTerms: Array of the search terms in all content languages
&$titleResult: Outparam; the value to return. A Title object or null.

'SearchGetNearMatchComplete': A chance to modify exact-title-matches in "go"
searches.
$term: Search term string
&$title: Current Title object that is being returned (null if none found).

'SearchResultInitFromTitle': Set the revision used when displaying a page in
search results.
$title: Current Title object being displayed in search results.
&$id: Revision ID (default is false, for latest)

'SearchIndexFields': Add fields to search index mapping.
&$fields: Array of fields, all implement SearchIndexField
$engine: SearchEngine instance for which mapping is being built.

'SearchDataForIndex': Add data to search document. Allows to add any data to
the field map used to index the document.
&$fields: Array of name => value pairs for fields
$handler: ContentHandler for the content being indexed
$page: WikiPage that is being indexed
$output: ParserOutput that is produced from the page
$engine: SearchEngine for which the indexing is intended

'SearchResultsAugment': Allows extension to add its code to the list of search
result augmentors.
&$setAugmentors: List of whole-set augmentor objects, must implement
  ResultSetAugmentor.
&$rowAugmentors: List of per-row augmentor objects, must implement
  ResultAugmentor.
Note that lists should be in the format name => object and the names in both
  lists should be distinct.

'SecondaryDataUpdates': Allows modification of the list of DataUpdates to
perform when page content is modified. Currently called by
AbstractContent::getSecondaryDataUpdates.
$title: Title of the page that is being edited.
$oldContent: Content object representing the page's content before the edit.
$recursive: bool indicating whether DataUpdates should trigger recursive
  updates (relevant mostly for LinksUpdate).
$parserOutput: ParserOutput representing the rendered version of the page
  after the edit.
&$updates: a list of DataUpdate objects, to be modified or replaced by
  the hook handler.

'SecuritySensitiveOperationStatus': Affect the return value from
MediaWiki\Auth\AuthManager::securitySensitiveOperationStatus().
&$status: (string) The status to be returned. One of the AuthManager::SEC_*
  constants. SEC_REAUTH will be automatically changed to SEC_FAIL if
  authentication isn't possible for the current session type.
$operation: (string) The operation being checked.
$session: (MediaWiki\Session\Session) The current session. The
  currently-authenticated user may be retrieved as $session->getUser().
$timeSinceAuth: (int) The time since last authentication. PHP_INT_MAX if
  the time of last auth is unknown, or -1 if authentication is not possible.

'SelfLinkBegin': Called before a link to the current article is displayed to
allow the display of the link to be customized.
$nt: the Title object
&$html: html to display for the link
&$trail: optional text to display before $html
&$prefix: optional text to display after $html
&$ret: the value to return if your hook returns false

'SendWatchlistEmailNotification': Return true to send watchlist email
notification
$targetUser: the user whom to send watchlist email notification
$title: the page title
$enotif: EmailNotification object

'SessionCheckInfo': Validate a MediaWiki\Session\SessionInfo as it's being
loaded from storage. Return false to prevent it from being used.
&$reason: String rejection reason to be logged
$info: MediaWiki\Session\SessionInfo being validated
$request: WebRequest being loaded from
$metadata: Array|false Metadata array for the MediaWiki\Session\Session
$data: Array|false Data array for the MediaWiki\Session\Session

'SessionMetadata': Add metadata to a session being saved.
$backend: MediaWiki\Session\SessionBackend being saved.
&$metadata: Array Metadata to be stored. Add new keys here.
$requests: Array of WebRequests potentially being saved to. Generally 0-1 real
  request and 0+ FauxRequests.

'SetupAfterCache': Called in Setup.php, after cache objects are set

'ShortPagesQuery': Allow extensions to modify the query used by
Special:ShortPages.
&$tables: tables to join in the query
&$conds: conditions for the query
&$joinConds: join conditions for the query
&$options: options for the query

'ShowMissingArticle': Called when generating the output for a non-existent page.
$article: The article object corresponding to the page

'ShowSearchHit': Customize display of search hit.
$searchPage: The SpecialSearch instance.
$result: The SearchResult to show
$terms: Search terms, for highlighting
&$link: HTML of link to the matching page. May be modified.
&$redirect: HTML of redirect info. May be modified.
&$section: HTML of matching section. May be modified.
&$extract: HTML of content extract. May be modified.
&$score: HTML of score. May be modified.
&$size: HTML of page size. May be modified.
&$date: HTML of of page modification date. May be modified.
&$related: HTML of additional info for the matching page. May be modified.
&$html: May be set to the full HTML that should be used to represent the search
  hit. Must include the <li> ... </li> tags. Will only be used if the hook
  function returned false.

'ShowSearchHitTitle': Customise display of search hit title/link.
&$title: Title to link to
&$titleSnippet: Label for the link representing the search result. Typically the
  article title.
$result: The SearchResult object
$terms: String of the search terms entered
$specialSearch: The SpecialSearch object
&$query: Array of query string parameters for the link representing the search
  result.
&$attributes: Array of title link attributes, can be modified by extension.

'SidebarBeforeOutput': Allows to edit sidebar just before it is output by skins.
Warning: This hook is run on each display. You should consider to use
'SkinBuildSidebar' that is aggressively cached.
$skin: Skin object
&$bar: Sidebar content
  Modify $bar to add or modify sidebar portlets.

'SiteNoticeAfter': After the sitenotice/anonnotice is composed.
&$siteNotice: HTML sitenotice. Alter the contents of $siteNotice to add to/alter
  the sitenotice/anonnotice.
$skin: Skin object

'SiteNoticeBefore': Before the sitenotice/anonnotice is composed. Return true to
allow the normal method of notice selection/rendering to work, or change the
value of $siteNotice and return false to alter it.
&$siteNotice: HTML returned as the sitenotice
$skin: Skin object

'SkinAfterBottomScripts': At the end of Skin::bottomScripts().
$skin: Skin object
&$text: bottomScripts Text. Append to $text to add additional text/scripts after
  the stock bottom scripts.

'SkinAfterContent': Allows extensions to add text after the page content and
article metadata. This hook should work in all skins. Set the &$data variable to
the text you're going to add.
&$data: (string) Text to be printed out directly (without parsing)
$skin: Skin object

'SkinBuildSidebar': At the end of Skin::buildSidebar().
$skin: Skin object
&$bar: Sidebar contents
Modify $bar to add or modify sidebar portlets.

'SkinCopyrightFooter': Allow for site and per-namespace customization of
copyright notice.
$title: displayed page title
$type: 'normal' or 'history' for old/diff views
&$msg: overridable message; usually 'copyright' or 'history_copyright'. This
  message must be in HTML format, not wikitext!
&$link: overridable HTML link to be passed into the message as $1
&$forContent: DEPRECATED! overridable flag if copyright footer is shown in
  content language.

'SkinEditSectionLinks': Modify the section edit links
$skin: Skin object rendering the UI
$title: Title object for the title being linked to (may not be the same as
  the page title, if the section is included from a template)
$section: The designation of the section being pointed to, to be included in
  the link, like "&section=$section"
$tooltip: The default tooltip.  Escape before using.
  By default, this is wrapped in the 'editsectionhint' message.
&$result: Array containing all link detail arrays. Each link detail array should
  contain the following keys:
    - targetTitle - Target Title object
    - text - String for the text
    - attribs - Array of attributes
    - query - Array of query parameters to add to the URL
    - options - Array of options for Linker::link
$lang: The language code to use for the link in the wfMessage function

'SkinGetPoweredBy': TODO
&$text: additional 'powered by' icons in HTML. Note: Modern skin does not use
  the MediaWiki icon but plain text instead.
$skin: Skin object

'SkinPreloadExistence': Supply titles that should be added to link existence
cache before the page is rendered.
&$titles: Array of Title objects
$skin: Skin object

'SkinSubPageSubtitle': At the beginning of Skin::subPageSubtitle().
If false is returned $subpages will be used instead of the HTML
subPageSubtitle() generates.
If true is returned, $subpages will be ignored and the rest of
subPageSubtitle() will run.
&$subpages: Subpage links HTML
$skin: Skin object
$out: OutputPage object

'SkinTemplateBuildNavUrlsNav_urlsAfterPermalink': After creating the "permanent
link" tab.
&$sktemplate: SkinTemplate object
&$nav_urls: array of tabs
&$revid: The revision id of the permanent link
&$revid2: The revision id of the permanent link, second time

'SkinTemplateGetLanguageLink': After building the data for a language link from
which the actual html is constructed.
&$languageLink: array containing data about the link. The following keys can be
  modified: href, text, title, class, lang, hreflang. Each of them is a string.
$languageLinkTitle: Title object belonging to the external language link.
$title: Title object of the page the link belongs to.
$outputPage: The OutputPage object the links are built from.

'SkinTemplateNavigation': Called on content pages after the tabs have been
added, but before variants have been added.
&$sktemplate: SkinTemplate object
&$links: Structured navigation links. This is used to alter the navigation for
  skins which use buildNavigationUrls such as Vector.

'SkinTemplateNavigation::SpecialPage': Called on special pages after the special
tab is added but before variants have been added.
&$sktemplate: SkinTemplate object
&$links: Structured navigation links. This is used to alter the navigation for
  skins which use buildNavigationUrls such as Vector.

'SkinTemplateNavigation::Universal': Called on both content and special pages
after variants have been added.
&$sktemplate: SkinTemplate object
&$links: Structured navigation links. This is used to alter the navigation for
  skins which use buildNavigationUrls such as Vector.

'SkinTemplateOutputPageBeforeExec': Before SkinTemplate::outputPage() starts
page output.
&$sktemplate: SkinTemplate object
&$tpl: QuickTemplate engine object

'SkinTemplatePreventOtherActiveTabs': Use this to prevent showing active tabs.
&$sktemplate: SkinTemplate object
&$res: set to true to prevent active tabs

'SkinTemplateTabAction': Override SkinTemplate::tabAction().
You can either create your own array, or alter the parameters for
the normal one.
&$sktemplate: The SkinTemplate instance.
$title: Title instance for the page.
$message: Visible label of tab.
$selected: Whether this is a selected tab.
$checkEdit: Whether or not the action=edit query should be added if appropriate.
&$classes: Array of CSS classes to apply.
&$query: Query string to add to link.
&$text: Link text.
&$result: Complete assoc. array if you want to return true.

'SkinTemplateToolboxEnd': Called by SkinTemplate skins after toolbox links have
been rendered (useful for adding more).
&$sk: The QuickTemplate based skin template running the hook.
$dummy: Called when SkinTemplateToolboxEnd is used from a BaseTemplate skin,
  extensions that add support for BaseTemplateToolbox should watch for this
  dummy parameter with "$dummy=false" in their code and return without echoing
  any HTML to avoid creating duplicate toolbox items.

'SoftwareInfo': Called by Special:Version for returning information about the
software.
&$software: The array of software in format 'name' => 'version'. See
  SpecialVersion::softwareInformation().

'SpecialBlockModifyFormFields': Add more fields to Special:Block
$sp: SpecialPage object, for context
&$fields: Current HTMLForm fields

'SpecialContributionsBeforeMainOutput': Before the form on Special:Contributions
$id: User id number, only provided for backwards-compatibility
$user: User object representing user contributions are being fetched for
$sp: SpecialPage instance, providing context

'SpecialContributions::formatRow::flags': Called before rendering a
Special:Contributions row.
$context: IContextSource object
$row: Revision information from the database
&$flags: List of flags on this row

'SpecialContributions::getForm::filters': Called with a list of filters to render
on Special:Contributions.
$sp: SpecialContributions object, for context
&$filters: List of filters rendered as HTML

'SpecialListusersDefaultQuery': Called right before the end of
UsersPager::getDefaultQuery().
$pager: The UsersPager instance
&$query: The query array to be returned

'SpecialListusersFormatRow': Called right before the end of
UsersPager::formatRow().
&$item: HTML to be returned. Will be wrapped in an <li> after the hook finishes
$row: Database row object

'SpecialListusersHeader': Called after adding the submit button in
UsersPager::getPageHeader().
$pager: The UsersPager instance
&$out: The header HTML

'SpecialListusersHeaderForm': Called before adding the submit button in
UsersPager::getPageHeader().
$pager: The UsersPager instance
&$out: The header HTML

'SpecialListusersQueryInfo': Called right before the end of.
UsersPager::getQueryInfo()
$pager: The UsersPager instance
&$query: The query array to be returned

'SpecialLogAddLogSearchRelations': Add log relations to the current log
$type: String of the log type
$request: WebRequest object for getting the value provided by the current user
&$qc: Array for query conditions to add

'SpecialMovepageAfterMove': Called after moving a page.
&$movePage: MovePageForm object
&$oldTitle: old title (object)
&$newTitle: new title (object)

'SpecialNewpagesConditions': Called when building sql query for
Special:NewPages.
&$special: NewPagesPager object (subclass of ReverseChronologicalPager)
$opts: FormOptions object containing special page options
&$conds: array of WHERE conditionals for query
&$tables: array of tables to be queried
&$fields: array of columns to select
&$join_conds: join conditions for the tables

'SpecialNewPagesFilters': Called after building form options at NewPages.
$special: the special page object
&$filters: associative array of filter definitions. The keys are the HTML
  name/URL parameters. Each key maps to an associative array with a 'msg'
  (message key) and a 'default' value.

'SpecialPage_initList': Called when setting up SpecialPageFactory::$list, use
this hook to remove a core special page or conditionally register special pages.
&$list: list (array) of core special pages

'SpecialPageAfterExecute': Called after SpecialPage::execute.
$special: the SpecialPage object
$subPage: the subpage string or null if no subpage was specified

'SpecialPageBeforeExecute': Called before SpecialPage::execute.
Return false to prevent execution.
$special: the SpecialPage object
$subPage: the subpage string or null if no subpage was specified

'SpecialPageBeforeFormDisplay': Before executing the HTMLForm object.
$name: name of the special page
&$form: HTMLForm object

'SpecialPasswordResetOnSubmit': When executing a form submission on
Special:PasswordReset.
&$users: array of User objects.
$data: array of data submitted by the user
&$error: string, error code (message key) used to describe to error (out
  parameter). The hook needs to return false when setting this, otherwise it
  will have no effect.

'SpecialRandomGetRandomTitle': Called during the execution of Special:Random,
use this to change some selection criteria or substitute a different title.
&$randstr: The random number from wfRandom()
&$isRedir: Boolean, whether to select a redirect or non-redirect
&$namespaces: An array of namespace indexes to get the title from
&$extra: An array of extra SQL statements
&$title: If the hook returns false, a Title object to use instead of the
  result from the normal query

'SpecialRecentChangesFilters': DEPRECATED since 1.23! Use
ChangesListSpecialPageStructuredFilters instead.
Called after building form options at RecentChanges.
$special: the special page object
&$filters: associative array of filter definitions. The keys are the HTML
  name/URL parameters. Each key maps to an associative array with a 'msg'
  (message key) and a 'default' value.

'SpecialRecentChangesPanel': Called when building form options in
SpecialRecentChanges.
&$extraOpts: array of added items, to which can be added
$opts: FormOptions for this request

'SpecialRecentChangesQuery': DEPRECATED since 1.23! Use
ChangesListSpecialPageStructuredFilters or ChangesListSpecialPageQuery instead.
Called when building SQL query for SpecialRecentChanges and
SpecialRecentChangesLinked.
&$conds: array of WHERE conditionals for query
&$tables: array of tables to be queried
&$join_conds: join conditions for the tables
$opts: FormOptions for this request
&$query_options: array of options for the database request
&$select: Array of columns to select

'SpecialResetTokensTokens': Called when building token list for
SpecialResetTokens.
&$tokens: array of token information arrays in the format of
        [
                'preference' => '<preference-name>',
                'label-message' => '<message-key>',
         ]

'SpecialSearchCreateLink': Called when making the message to create a page or
go to the existing page.
$t: title object searched for
&$params: an array of the default message name and page title (as parameter)

'SpecialSearchGoResult': If a hook returns false the 'go' feature will be
canceled and a normal search will be performed. Returning true without setting
$url does a standard redirect to $title. Setting $url redirects to the
specified URL.
$term: The string the user searched for
$title: The title the 'go' feature has decided to forward the user to
&$url: Initially null, hook subscribers can set this to specify the final url to
  redirect to

'SpecialSearchNogomatch': Called when the 'Go' feature is triggered (generally
from autocomplete search other than the main bar on Special:Search) and the
target doesn't exist. Full text search results are generated after this hook is
called.
&$title: title object generated from the text entered by the user

'SpecialSearchPowerBox': The equivalent of SpecialSearchProfileForm for
the advanced form, a.k.a. power search box.
&$showSections: an array to add values with more options to
$term: the search term (not a title object)
$opts: an array of hidden options (containing 'redirs' and 'profile')

'SpecialSearchProfileForm': Allows modification of search profile forms.
$search: special page object
&$form: String: form html
$profile: String: current search profile
$term: String: search term
$opts: Array: key => value of hidden options for inclusion in custom forms

'SpecialSearchProfiles': Allows modification of search profiles.
&$profiles: profiles, which can be modified.

'SpecialSearchResults': Called before search result display
$term: string of search term
&$titleMatches: empty or SearchResultSet object
&$textMatches: empty or SearchResultSet object

'SpecialSearchResultsPrepend': Called immediately before returning HTML
on the search results page.  Useful for including an external search
provider.  To disable the output of MediaWiki search output, return
false.
$specialSearch: SpecialSearch object ($this)
$output: $wgOut
$term: Search term specified by the user

'SpecialSearchResultsAppend': Called immediately before returning HTML
on the search results page.  Useful for including a feedback link.
$specialSearch: SpecialSearch object ($this)
$output: $wgOut
$term: Search term specified by the user

'SpecialSearchSetupEngine': Allows passing custom data to search engine.
$search: SpecialSearch special page object
$profile: String: current search profile
$engine: the search engine

'SpecialStatsAddExtra': Add extra statistic at the end of Special:Statistics.
&$extraStats: Array to save the new stats
        $extraStats['<name of statistic>'] => <value>;
  <value> can be an array with the keys "name" and "number":
  "name" is the HTML to be displayed in the name column
  "number" is the number to be displayed.
  or, <value> can be the number to be displayed and <name> is the
  message key to use in the name column,
$context: IContextSource object

'SpecialTrackingCategories::preprocess': Called after LinkBatch on
Special:TrackingCategories
$specialPage: The SpecialTrackingCategories object
$trackingCategories: Array of data from Special:TrackingCategories with msg and
  cats

'SpecialTrackingCategories::generateCatLink': Called for each cat link on
Special:TrackingCategories
$specialPage: The SpecialTrackingCategories object
$catTitle: The Title object of the linked category
&$html: The Result html

'SpecialUploadComplete': Called after successfully uploading a file from
Special:Upload.
&$form: The SpecialUpload object

'SpecialVersionVersionUrl': Called when building the URL for Special:Version.
$wgVersion: Current $wgVersion for you to use
&$versionUrl: Raw url to link to (eg: release notes)

'SpecialWatchlistFilters': DEPRECATED since 1.23! Use
ChangesListSpecialPageStructuredFilters instead.
Called after building form options at Watchlist.
$special: the special page object
&$filters: associative array of filter definitions. The keys are the HTML
  name/URL parameters. Each key maps to an associative array with a 'msg'
  (message key) and a 'default' value.

'SpecialWatchlistGetNonRevisionTypes': Called when building sql query for
SpecialWatchlist. Allows extensions to register custom values they have
inserted to rc_type so they can be returned as part of the watchlist.
&$nonRevisionTypes: array of values in the rc_type field of recentchanges table

'SpecialWatchlistQuery': DEPRECATED since 1.23! Use
ChangesListSpecialPageStructuredFilters or ChangesListSpecialPageQuery instead.
Called when building sql query for SpecialWatchlist.
&$conds: array of WHERE conditionals for query
&$tables: array of tables to be queried
&$join_conds: join conditions for the tables
&$fields: array of query fields
$opts: A FormOptions object with watchlist options for the current request

'TestCanonicalRedirect': Called when about to force a redirect to a canonical
URL for a title when we have no other parameters on the URL. Gives a chance for
extensions that alter page view behavior radically to abort that redirect or
handle it manually.
$request: WebRequest
$title: Title of the currently found title obj
$output: OutputPage object

'ThumbnailBeforeProduceHTML': Called before an image HTML is about to be
rendered (by ThumbnailImage:toHtml method).
$thumbnail: the ThumbnailImage object
&$attribs: image attribute array
&$linkAttribs: image link attribute array

'TitleArrayFromResult': Called when creating an TitleArray object from a
database result.
&$titleArray: set this to an object to override the default object returned
$res: database result used to create the object

'TitleExists': Called when determining whether a page exists at a given title.
$title: The title being tested.
&$exists: Whether the title exists.

'TitleGetEditNotices': Allows extensions to add edit notices
$title: The Title object for the page the edit notices are for
$oldid: Revision ID that the edit notices are for (or 0 for latest)
&$notices: Array of notices. Keys are i18n message keys, values are
parseAsBlock()ed messages.

'TitleGetRestrictionTypes': Allows extensions to modify the types of protection
that can be applied.
$title: The title in question.
&$types: The types of protection available.

'TitleIsAlwaysKnown': Called when determining if a page exists. Allows
overriding default behavior for determining if a page exists. If $isKnown is
kept as null, regular checks happen. If it's a boolean, this value is returned
by the isKnown method.
$title: Title object that is being checked
&$isKnown: Boolean|null; whether MediaWiki currently thinks this page is known

'TitleIsMovable': Called when determining if it is possible to move a page. Note
that this hook is not called for interwiki pages or pages in immovable
namespaces: for these, isMovable() always returns false.
$title: Title object that is being checked
&$result: Boolean; whether MediaWiki currently thinks this page is movable.
  Hooks may change this value to override the return value of
  Title::isMovable().


'TitleMove': Before moving an article (title).
$old: old title
$nt: new title
$user: user who does the move

'TitleMoveStarting': Before moving an article (title), but just after the atomic
DB section starts.
$old: old title
$nt: new title
$user: user who does the move

'TitleMoveComplete': After moving an article (title), post-commit.
&$old: old title
&$nt: new title
&$user: user who did the move
$pageid: database ID of the page that's been moved
$redirid: database ID of the created redirect
$reason: reason for the move
$revision: the Revision created by the move

'TitleMoveCompleting': After moving an article (title), pre-commit.
$old: old title
$nt: new title
$user: user who did the move
$pageid: database ID of the page that's been moved
$redirid: database ID of the created redirect
$reason: reason for the move
$revision: the Revision created by the move

'TitleQuickPermissions': Called from Title::checkQuickPermissions to add to
or override the quick permissions check.
$title: The Title object being accessed
$user: The User performing the action
$action: Action being performed
&$errors: Array of errors
$doExpensiveQueries: Whether to do expensive DB queries
$short: Whether to return immediately on first error

'TitleReadWhitelist': Called at the end of read permissions checks, just before
adding the default error message if nothing allows the user to read the page. If
a handler wants a title to *not* be whitelisted, it should also return false.
$title: Title object being checked against
$user: Current user object
&$whitelisted: Boolean value of whether this title is whitelisted

'TitleSquidURLs': Called to determine which URLs to purge from HTTP caches.
$title: Title object to purge
&$urls: An array of URLs to purge from the caches, to be manipulated.

'UnblockUser': Before an IP address or user is unblocked.
&$block: The Block object about to be saved
&$user: The user performing the unblock (not the one being unblocked)
&$reason: If the hook is aborted, the error message to be returned in an array

'UnblockUserComplete': After an IP address or user has been unblocked.
$block: The Block object that was saved
$user: The user who performed the unblock (not the one being unblocked)

'UndeleteForm::showHistory': Called in UndeleteForm::showHistory, after a
PageArchive object has been created but before any further processing is done.
&$archive: PageArchive object
$title: Title object of the page that we're viewing

'UndeleteForm::showRevision': Called in UndeleteForm::showRevision, after a
PageArchive object has been created but before any further processing is done.
&$archive: PageArchive object
$title: Title object of the page that we're viewing

'UndeleteForm::undelete': Called in UndeleteForm::undelete, after checking that
the site is not in read-only mode, that the Title object is not null and after
a PageArchive object has been constructed but before performing any further
processing.
&$archive: PageArchive object
$title: Title object of the page that we're about to undelete

'UndeleteShowRevision': Called when showing a revision in Special:Undelete.
$title: title object related to the revision
$rev: revision (object) that will be viewed

'UnitTestsAfterDatabaseSetup': Called right after MediaWiki's test
infrastructure has finished creating/duplicating core tables for unit tests.
$database: Database in question
$prefix: Table prefix to be used in unit tests

'UnitTestsBeforeDatabaseTeardown': Called right before MediaWiki tears down its
database infrastructure used for unit tests.

'UnitTestsList': Called when building a list of paths containing PHPUnit tests.
Since 1.24: Paths pointing to a directory will be recursively scanned for
test case files matching the suffix "Test.php".
&$paths: list of test cases and directories to search.

'UnknownAction': DEPRECATED since 1.19! To add an action in an extension,
create a subclass of Action, and add a new key to $wgActions.
An unknown "action" has occurred (useful for defining your own actions).
$action: action name
$article: article "acted on"

'UnwatchArticle': Before a watch is removed from an article.
&$user: user watching
&$page: WikiPage object to be removed
&$status: Status object to be returned if the hook returns false

'UnwatchArticleComplete': After a watch is removed from an article.
$user: user that watched
&$page: WikiPage object that was watched

'UpdateUserMailerFormattedPageStatus': Before notification email gets sent.
&$formattedPageStatus: list of valid page states

'UploadComplete': Upon completion of a file upload.
&$uploadBase: UploadBase (or subclass) object. File can be accessed by
  $uploadBase->getLocalFile().

'UploadCreateFromRequest': When UploadBase::createFromRequest has been called.
$type: (string) the requested upload type
&$className: the class name of the Upload instance to be created

'UploadForm:BeforeProcessing': At the beginning of processUpload(). Lets you
poke at member variables like $mUploadDescription before the file is saved. Do
not use this hook to break upload processing. This will return the user to a
blank form with no error message; use UploadVerification and UploadVerifyFile
instead.
&$form: UploadForm object

'UploadForm:getInitialPageText': After the initial page text for file uploads
is generated, to allow it to be altered.
&$pageText: the page text
$msg: array of header messages
$config: Config object

'UploadForm:initial': Before the upload form is generated. You might set the
member-variables $uploadFormTextTop and $uploadFormTextAfterSummary to inject
text (HTML) either before or after the editform.
&$form: UploadForm object

'UploadFormInitDescriptor': After the descriptor for the upload form as been
assembled.
&$descriptor: (array) the HTMLForm descriptor

'UploadFormSourceDescriptors': after the standard source inputs have been
added to the descriptor
&$descriptor: (array) the HTMLForm descriptor
&$radio: Boolean, if source type should be shown as radio button
$selectedSourceType: The selected source type

'UploadStashFile': Before a file is stashed (uploaded to stash).
Note that code which has not been updated for MediaWiki 1.28 may not call this
hook. If your extension absolutely, positively must prevent some files from
being uploaded, use UploadVerifyFile or UploadVerifyUpload.
$upload: (object) An instance of UploadBase, with all info about the upload
$user: (object) An instance of User, the user uploading this file
$props: (array) File properties, as returned by FSFile::getPropsFromPath()
&$error: output: If the file stashing should be prevented, set this to the
  reason in the form of [ messagename, param1, param2, ... ] or a
  MessageSpecifier instance (you might want to use ApiMessage to provide machine
  -readable details for the API).

'UploadVerification': DEPRECATED since 1.28! Use UploadVerifyFile instead.
Additional chances to reject an uploaded file.
$saveName: (string) destination file name
$tempName: (string) filesystem path to the temporary file for checks
&$error: (string) output: message key for message to show if upload canceled by
  returning false. May also be an array, where the first element is the message
  key and the remaining elements are used as parameters to the message.

'UploadVerifyFile': extra file verification, based on MIME type, etc. Preferred
in most cases over UploadVerification.
$upload: (object) an instance of UploadBase, with all info about the upload
$mime: (string) The uploaded file's MIME type, as detected by MediaWiki.
  Handlers will typically only apply for specific MIME types.
&$error: (object) output: true if the file is valid. Otherwise, set this to the
  reason in the form of [ messagename, param1, param2, ... ] or a
  MessageSpecifier instance (you might want to use ApiMessage to provide machine
  -readable details for the API).

'UploadVerifyUpload': Upload verification, based on both file properties like
MIME type (same as UploadVerifyFile) and the information entered by the user
(upload comment, file page contents etc.).
$upload: (object) An instance of UploadBase, with all info about the upload
$user: (object) An instance of User, the user uploading this file
$props: (array) File properties, as returned by FSFile::getPropsFromPath()
$comment: (string) Upload log comment (also used as edit summary)
$pageText: (string) File description page text (only used for new uploads)
&$error: output: If the file upload should be prevented, set this to the reason
  in the form of [ messagename, param1, param2, ... ] or a MessageSpecifier
  instance (you might want to use ApiMessage to provide machine-readable details
  for the API).

'UserIsBot': when determining whether a user is a bot account
$user: the user
&$isBot: whether this is user a bot or not (boolean)

'User::mailPasswordInternal': before creation and mailing of a user's new
temporary password
&$user: the user who sent the message out
&$ip: IP of the user who sent the message out
&$u: the account whose new password will be set

'UserAddGroup': Called when adding a group or changing a group's expiry; return
false to override stock group addition.
$user: the user object that is to have a group added
&$group: the group to add; can be modified
&$expiry: the expiry time in TS_MW format, or null if the group is not to
expire; can be modified

'UserArrayFromResult': Called when creating an UserArray object from a database
result.
&$userArray: set this to an object to override the default object returned
$res: database result used to create the object

'userCan': To interrupt/advise the "user can do X to Y article" check. If you
want to display an error message, try getUserPermissionsErrors.
&$title: Title object being checked against
&$user: Current user object
$action: Action being checked
&$result: Pointer to result returned if hook returns false. If null is returned,
  userCan checks are continued by internal code.

'UserCanSendEmail': To override User::canSendEmail() permission check.
&$user: User (object) whose permission is being checked
&$canSend: bool set on input, can override on output

'UserClearNewTalkNotification': Called when clearing the "You have new
messages!" message, return false to not delete it.
&$user: User (object) that will clear the message
$oldid: ID of the talk page revision being viewed (0 means the most recent one)

'UserCreateForm': DEPRECATED since 1.27! Create an AuthenticationProvider
instead. Manipulate the login form.
&$template: SimpleTemplate instance for the form

'UserEffectiveGroups': Called in User::getEffectiveGroups().
&$user: User to get groups for
&$groups: Current effective groups

'UserGetAllRights': After calculating a list of all available rights.
&$rights: Array of rights, which may be added to.

'UserGetDefaultOptions': After fetching the core default, this hook is run right
before returning the options to the caller. Warning: This hook is called for
every call to User::getDefaultOptions(), which means it's potentially called
dozens or hundreds of times. You may want to cache the results of non-trivial
operations in your hook function for this reason.
&$defaultOptions: Array of preference keys and their default values.

'UserGetEmail': Called when getting an user email address.
$user: User object
&$email: email, change this to override local email

'UserGetEmailAuthenticationTimestamp': Called when getting the timestamp of
email authentication.
$user: User object
&$timestamp: timestamp, change this to override local email authentication
  timestamp

'UserGetImplicitGroups': DEPRECATED since 1.25!
Called in User::getImplicitGroups().
&$groups: List of implicit (automatically-assigned) groups

'UserGetLanguageObject': Called when getting user's interface language object.
$user: User object
&$code: Language code that will be used to create the object
$context: IContextSource object

'UserGetReservedNames': Allows to modify $wgReservedUsernames at run time.
&$reservedUsernames: $wgReservedUsernames

'UserGetRights': Called in User::getRights().
$user: User to get rights for
&$rights: Current rights

'UserGroupsChanged': Called after user groups are changed.
$user: User whose groups changed
$added: Groups added
$removed: Groups removed
$performer: User who performed the change, false if via autopromotion
$reason: The reason, if any, given by the user performing the change,
false if via autopromotion.
$oldUGMs: An associative array (group name => UserGroupMembership object) of
the user's group memberships before the change.
$newUGMs: An associative array (group name => UserGroupMembership object) of
the user's current group memberships.

'UserIsBlockedFrom': Check if a user is blocked from a specific page (for
specific block exemptions).
$user: User in question
$title: Title of the page in question
&$blocked: Out-param, whether or not the user is blocked from that page.
&$allowUsertalk: If the user is blocked, whether or not the block allows users
  to edit their own user talk pages.

'UserIsBlockedGlobally': Check if user is blocked on all wikis.
&$user: User object
$ip: User's IP address
&$blocked: Whether the user is blocked, to be modified by the hook
&$block: The Block object, to be modified by the hook

'UserIsEveryoneAllowed': Check if all users are allowed some user right; return
false if a UserGetRights hook might remove the named right.
$right: The user right being checked

'UserIsHidden': Check if the user's name should be hidden. See User::isHidden().
$user: User in question.
&$hidden: Set true if the user's name should be hidden.

'UserIsLocked': Check if the user is locked. See User::isLocked().
$user: User in question.
&$locked: Set true if the user should be locked.

'UserLoadAfterLoadFromSession': Called to authenticate users on external or
environmental means; occurs after session is loaded.
$user: user object being loaded

'UserLoadDefaults': Called when loading a default user.
$user: user object
$name: user name

'UserLoadFromDatabase': Called when loading a user from the database.
$user: user object
&$s: database query object

'UserLoadFromSession': DEPRECATED since 1.27! Create a
MediaWiki\Session\SessionProvider instead.
Called to authenticate users on external/environmental means; occurs before
session is loaded.
$user: user object being loaded
&$result: set this to a boolean value to abort the normal authentication
  process

'UserLoadOptions': When user options/preferences are being loaded from the
database.
$user: User object
&$options: Options, can be modified.

'UserLoggedIn': Called after a user is logged in
$user: User object for the logged-in user

'UserLoginComplete': Show custom content after a user has logged in via the Web
interface. For functionality that needs to run after any login (API or web) use
UserLoggedIn.
&$user: the user object that was created on login
&$inject_html: Any HTML to inject after the "logged in" message.
$direct: (bool) The hook is called directly after a successful login. This will
  only happen once per login. A UserLoginComplete call with direct=false can
  happen when the user visits the login page while already logged in.

'UserLoginForm': DEPRECATED since 1.27! Create an AuthenticationProvider
instead. Manipulate the login form.
&$template: QuickTemplate instance for the form

'UserLogout': Before a user logs out.
&$user: the user object that is about to be logged out

'UserLogoutComplete': After a user has logged out.
&$user: the user object _after_ logout (won't have name, ID, etc.)
&$inject_html: Any HTML to inject after the "logged out" message.
$oldName: name of the user before logout (string)

'UserMailerChangeReturnPath': Called to generate a VERP return address
when UserMailer sends an email, with a bounce handling extension.
$to: Array of MailAddress objects for the recipients
&$returnPath: The return address string

'UserMailerSplitTo': Called in UserMailer::send() to give extensions a chance
to split up an email with multiple the To: field into separate emails.
&$to: array of MailAddress objects; unset the ones which should be mailed
separately

'UserMailerTransformContent': Called in UserMailer::send() to change email
contents. Extensions can block sending the email by returning false and setting
$error.
$to: array of MailAdresses of the targets
$from: MailAddress of the sender
&$body: email body, either a string (for plaintext emails) or an array with
  'text' and 'html' keys
&$error: should be set to an error message string

'UserMailerTransformMessage': Called in UserMailer::send() to change email after
it has gone through the MIME transform. Extensions can block sending the email
by returning false and setting $error.
$to: array of MailAdresses of the targets
$from: MailAddress of the sender
&$subject: email subject (not MIME encoded)
&$headers: email headers (except To: and Subject:) as an array of header
name => value pairs
&$body: email body (in MIME format) as a string
&$error: should be set to an error message string

'UserRemoveGroup': Called when removing a group; return false to override stock
group removal.
$user: the user object that is to have a group removed
&$group: the group to be removed, can be modified

'UserRequiresHTTPS': Called to determine whether a user needs
to be switched to HTTPS.
$user: User in question.
&$https: Boolean whether $user should be switched to HTTPS.

'UserResetAllOptions': Called in User::resetOptions() when user preferences
have been requested to be reset. This hook can be used to exclude certain
options from being reset even when the user has requested all prefs to be reset,
because certain options might be stored in the user_properties database table
despite not being visible and editable via Special:Preferences.
$user: the User (object) whose preferences are being reset
&$newOptions: array of new (site default) preferences
$options: array of the user's old preferences
$resetKinds: array containing the kinds of preferences to reset

'UserRetrieveNewTalks': Called when retrieving "You have new messages!"
message(s).
&$user: user retrieving new talks messages
&$talks: array of new talks page(s)

'UserRights': DEPRECATED since 1.26! Use UserGroupsChanged instead.
After a user's group memberships are changed.
&$user: User object that was changed
$add: Array of strings corresponding to groups added
$remove: Array of strings corresponding to groups removed

'UserSaveOptions': Called just before saving user preferences. Hook handlers can
either add or manipulate options, or reset one back to it's default to block
changing it. Hook handlers are also allowed to abort the process by returning
false, e.g. to save to a global profile instead. Compare to the UserSaveSettings
hook, which is called after the preferences have been saved.
$user: The User for which the options are going to be saved
&$options: The users options as an associative array, modifiable

'UserSaveSettings': Called directly after user preferences (user_properties in
the database) have been saved. Compare to the UserSaveOptions hook, which is
called before.
$user: The User for which the options have been saved

'UserSetCookies': DEPRECATED since 1.27! If you're trying to replace core
session cookie handling, you want to create a subclass of
MediaWiki\Session\CookieSessionProvider instead. Otherwise, you can no longer
count on user data being saved to cookies versus some other mechanism.
Called when setting user cookies.
$user: User object
&$session: session array, will be added to the session
&$cookies: cookies array mapping cookie name to its value

'UserSetEmail': Called when changing user email address.
$user: User object
&$email: new email, change this to override new email address

'UserSetEmailAuthenticationTimestamp': Called when setting the timestamp of
email authentication.
$user: User object
&$timestamp: new timestamp, change this to override local email
authentication timestamp

'UserToolLinksEdit': Called when generating a list of user tool links, e.g.
"Foobar (Talk | Contribs | Block)".
$userId: User id of the current user
$userText: User name of the current user
&$items: Array of user tool links as HTML fragments

'UsersPagerDoBatchLookups': Called in UsersPager::doBatchLookups() to give
extensions providing user group data from an alternate source a chance to add
their data into the cache array so that things like global user groups are
displayed correctly in Special:ListUsers.
$dbr: Read-only database handle
$userIds: Array of user IDs whose groups we should look up
&$cache: Array of user ID -> (array of internal group name (e.g. 'sysop') ->
  UserGroupMembership object)
&$groups: Array of group name -> bool true mappings for members of a given user
group

'ValidateExtendedMetadataCache': Called to validate the cached metadata in
FormatMetadata::getExtendedMeta (return false means cache will be
invalidated and GetExtendedMetadata hook called again).
$timestamp: The timestamp metadata was generated
$file: The file the metadata is for

'WantedPages::getQueryInfo': Called in WantedPagesPage::getQueryInfo(), can be
used to alter the SQL query which gets the list of wanted pages.
&$wantedPages: WantedPagesPage object
&$query: query array, see QueryPage::getQueryInfo() for format documentation

'WatchArticle': Before a watch is added to an article.
&$user: user that will watch
&$page: WikiPage object to be watched
&$status: Status object to be returned if the hook returns false

'WatchArticleComplete': After a watch is added to an article.
&$user: user that watched
&$page: WikiPage object watched

'WatchedItemQueryServiceExtensions': Create a WatchedItemQueryServiceExtension.
&$extensions: Add WatchedItemQueryServiceExtension objects to this array
$watchedItemQueryService: Service object

'WatchlistEditorBeforeFormRender': Before building the Special:EditWatchlist
form, used to manipulate the list of pages or preload data based on that list.
&$watchlistInfo: array of watchlisted pages in
  [namespaceId => ['title1' => 1, 'title2' => 1]] format

'WatchlistEditorBuildRemoveLine': when building remove lines in
Special:Watchlist/edit.
&$tools: array of extra links
$title: Title object
$redirect: whether the page is a redirect
$skin: Skin object
&$link: HTML link to title

'WebRequestPathInfoRouter': While building the PathRouter to parse the
REQUEST_URI.
$router: The PathRouter instance

'WebResponseSetCookie': when setting a cookie in WebResponse::setcookie().
Return false to prevent setting of the cookie.
&$name: Cookie name passed to WebResponse::setcookie()
&$value: Cookie value passed to WebResponse::setcookie()
&$expire: Cookie expiration, as for PHP's setcookie()
&$options: Options passed to WebResponse::setcookie()

'wfShellWikiCmd': Called when generating a shell-escaped command line string to
run a MediaWiki cli script.
&$script: MediaWiki cli script path
&$parameters: Array of arguments and options to the script
&$options: Associative array of options, may contain the 'php' and 'wrapper'
  keys

'wgQueryPages': Called when initialising list of QueryPage subclasses, use this
to add new query pages to be updated with maintenance/updateSpecialPages.php.
&$qp: The list of QueryPages

'WhatLinksHereProps': Allows annotations to be added to WhatLinksHere
$row: The DB row of the entry.
$title: The Title of the page where the link comes FROM
$target: The Title of the page where the link goes TO
&$props: Array of HTML strings to display after the title.

'WikiExporter::dumpStableQuery': Get the SELECT query for "stable" revisions
dumps. One, and only one hook should set this, and return false.
&$tables: Database tables to use in the SELECT query
&$opts: Options to use for the query
&$join: Join conditions

'WikiPageDeletionUpdates': manipulate the list of DeferrableUpdates to be
applied when a page is deleted. Called in WikiPage::getDeletionUpdates(). Note
that updates specific to a content model should be provided by the respective
Content's getDeletionUpdates() method.
$page: the WikiPage
$content: the Content to generate updates for, or null in case the page revision
  could not be loaded. The delete will succeed despite this.
&$updates: the array of objects that implement DeferrableUpdate. Hook function
  may want to add to it.

'WikiPageFactory': Override WikiPage class used for a title
$title: Title of the page
&$page: Variable to set the created WikiPage to.

'XmlDumpWriterOpenPage': Called at the end of XmlDumpWriter::openPage, to allow
extra metadata to be added.
$obj: The XmlDumpWriter object.
&$out: The output string.
$row: The database row for the page.
$title: The title of the page.

'XmlDumpWriterWriteRevision': Called at the end of a revision in an XML dump, to
add extra metadata.
&$obj: The XmlDumpWriter object.
&$out: The text being output.
$row: The database row for the revision.
$text: The revision text.

More hooks might be available but undocumented, you can execute
"php maintenance/findHooks.php" to find hidden ones.