3 This document describes how event hooks work in MediaWiki; how to add
4 hooks for an event; and how to run hooks for an event.
9 Something that happens with the wiki. For example: a user logs
10 in. A wiki page is saved. A wiki page is deleted. Often there are
11 two events associated with a single action: one before the code
12 is run to make the event happen, and one after. Each event has a
13 name, preferably in CamelCase. For example, 'UserLogin',
14 'ArticleSave', 'ArticleSaveComplete', 'ArticleDelete'.
17 A clump of code and data that should be run when an event
18 happens. This can be either a function and a chunk of data, or an
22 The function part of a hook.
26 Hooks allow us to decouple optionally-run code from code that is run
27 for everyone. It allows MediaWiki hackers, third-party developers and
28 local administrators to define code that will be run at certain points
29 in the mainline code, and to modify the data run by that mainline
30 code. Hooks can keep mainline code simple, and make it easier to
31 write extensions. Hooks are a principled alternative to local patches.
33 Consider, for example, two options in MediaWiki. One reverses the
34 order of a title before displaying the article; the other converts the
35 title to all uppercase letters. Currently, in MediaWiki code, we
36 would handle this as follows (note: not real code, here):
38 function showAnArticle($article) {
39 global $wgReverseTitle, $wgCapitalizeTitle;
41 if ($wgReverseTitle) {
42 wfReverseTitle($article);
45 if ($wgCapitalizeTitle) {
46 wfCapitalizeTitle($article);
49 # code to actually show the article goes here
52 An extension writer, or a local admin, will often add custom code to
53 the function -- with or without a global variable. For example,
54 someone wanting email notification when an article is shown may add:
56 function showAnArticle($article) {
57 global $wgReverseTitle, $wgCapitalizeTitle;
59 if ($wgReverseTitle) {
60 wfReverseTitle($article);
63 if ($wgCapitalizeTitle) {
64 wfCapitalizeTitle($article);
67 # code to actually show the article goes here
69 if ($wgNotifyArticle) {
70 wfNotifyArticleShow($article));
74 Using a hook-running strategy, we can avoid having all this
75 option-specific stuff in our mainline code. Using hooks, the function
78 function showAnArticle($article) {
80 if (wfRunHooks('ArticleShow', array(&$article))) {
82 # code to actually show the article goes here
84 wfRunHooks('ArticleShowComplete', array(&$article));
88 We've cleaned up the code here by removing clumps of weird,
89 infrequently used code and moving them off somewhere else. It's much
90 easier for someone working with this code to see what's _really_ going
91 on, and make changes or fix bugs.
93 In addition, we can take all the code that deals with the little-used
94 title-reversing options (say) and put it in one place. Instead of
95 having little title-reversing if-blocks spread all over the codebase
96 in showAnArticle, deleteAnArticle, exportArticle, etc., we can
97 concentrate it all in an extension file:
99 function reverseArticleTitle($article) {
103 function reverseForExport($article) {
107 The setup function for the extension just has to add its hook
108 functions to the appropriate events:
110 setupTitleReversingExtension() {
113 $wgHooks['ArticleShow'][] = 'reverseArticleTitle';
114 $wgHooks['ArticleDelete'][] = 'reverseArticleTitle';
115 $wgHooks['ArticleExport'][] = 'reverseForExport';
118 Having all this code related to the title-reversion option in one
119 place means that it's easier to read and understand; you don't have to
120 do a grep-find to see where the $wgReverseTitle variable is used, say.
122 If the code is well enough isolated, it can even be excluded when not
123 used -- making for some slight savings in memory and load-up
124 performance at runtime. Admins who want to have all the reversed
127 require_once('extensions/ReverseTitle.php');
129 ...to their LocalSettings.php file; those of us who don't want or need
130 it can just leave it out.
132 The extensions don't even have to be shipped with MediaWiki; they
133 could be provided by a third-party developer or written by the admin
138 A hook is a chunk of code run at some particular event. It consists of:
140 * a function with some optional accompanying data, or
141 * an object with a method and some optional accompanying data.
143 Hooks are registered by adding them to the global $wgHooks array for a
144 given event. All the following are valid ways to define hooks:
146 $wgHooks['EventName'][] = 'someFunction'; # function, no data
147 $wgHooks['EventName'][] = array('someFunction', $someData);
148 $wgHooks['EventName'][] = array('someFunction'); # weird, but OK
150 $wgHooks['EventName'][] = $object; # object only
151 $wgHooks['EventName'][] = array($object, 'someMethod');
152 $wgHooks['EventName'][] = array($object, 'someMethod', $someData);
153 $wgHooks['EventName'][] = array($object); # weird but OK
155 When an event occurs, the function (or object method) will be called
156 with the optional data provided as well as event-specific parameters.
157 The above examples would result in the following code being executed
158 when 'EventName' happened:
161 someFunction($param1, $param2)
163 someFunction($someData, $param1, $param2)
166 $object->onEventName($param1, $param2)
168 $object->someMethod($param1, $param2)
169 # object with method and data
170 $object->someMethod($someData, $param1, $param2)
172 Note that when an object is the hook, and there's no specified method,
173 the default method called is 'onEventName'. For different events this
174 would be different: 'onArticleSave', 'onUserLogin', etc.
176 The extra data is useful if we want to use the same function or object
177 for different purposes. For example:
179 $wgHooks['ArticleSaveComplete'][] = array('ircNotify', 'TimStarling');
180 $wgHooks['ArticleSaveComplete'][] = array('ircNotify', 'brion');
182 This code would result in ircNotify being run twice when an article is
183 saved: once for 'TimStarling', and once for 'brion'.
185 Hooks can return three possible values:
187 * true: the hook has operated successfully
188 * "some string": an error occurred; processing should
189 stop and the error should be shown to the user
190 * false: the hook has successfully done the work
191 necessary and the calling function should skip
193 The last result would be for cases where the hook function replaces
194 the main functionality. For example, if you wanted to authenticate
195 users to a custom system (LDAP, another PHP program, whatever), you
198 $wgHooks['UserLogin'][] = array('ldapLogin', $ldapServer);
200 function ldapLogin($username, $password) {
205 Returning false makes less sense for events where the action is
206 complete, and will normally be ignored.
210 A calling function or method uses the wfRunHooks() function to run
211 the hooks related to a particular event, like so:
217 if (wfRunHooks('ArticleProtect', array(&$this, &$wgUser))) {
218 # protect the article
219 wfRunHooks('ArticleProtectComplete', array(&$this, &$wgUser));
224 wfRunHooks() returns true if the calling function should continue
225 processing (the hooks ran OK, or there are no hooks to run), or false
226 if it shouldn't (an error occurred, or one of the hooks handled the
227 action already). Checking the return value matters more for "before"
228 hooks than for "complete" hooks.
230 Note that hook parameters are passed in an array; this is a necessary
231 inconvenience to make it possible to pass reference values (that can
232 be changed) into the hook code. Also note that earlier versions of
233 wfRunHooks took a variable number of arguments; the array() calling
234 protocol came about after MediaWiki 1.4rc1.
236 ==Events and parameters==
238 This is a list of known events and parameters; please add to it if
239 you're going to add events to the MediaWiki code.
241 'AbortLogin': Return false to cancel account login.
242 $user: the User object being authenticated against
243 $password: the password being submitted, not yet checked for validity
244 &$retval: a LoginForm class constant to return from authenticateUserData();
245 default is LoginForm::ABORTED. Note that the client may be using
246 a machine API rather than the HTML user interface.
248 'AbortNewAccount': Return false to cancel account creation.
249 $user: the User object about to be created (read-only, incomplete)
250 $message: out parameter: error message to display on abort
252 'AddNewAccount': after a user account is created
253 $user: the User object that was created. (Parameter added in 1.7)
255 'AlternateEdit': before checking if an user can edit a page and
256 before showing the edit form ( EditPage::edit() ). This is triggered
258 $EditPage : the EditPage object
260 'ArticleDelete': before an article is deleted
261 $article: the article (object) being deleted
262 $user: the user (object) deleting the article
263 $reason: the reason (string) the article is being deleted
265 'ArticleDeleteComplete': after an article is deleted
266 $article: the article that was deleted
267 $user: the user that deleted the article
268 $reason: the reason the article was deleted
270 'ArticleProtect': before an article is protected
271 $article: the article being protected
272 $user: the user doing the protection
273 $protect: boolean whether this is a protect or an unprotect
274 $reason: Reason for protect
275 $moveonly: boolean whether this is for move only or not
277 'ArticleProtectComplete': after an article is protected
278 $article: the article that was protected
279 $user: the user who did the protection
280 $protect: boolean whether it was a protect or an unprotect
281 $reason: Reason for protect
282 $moveonly: boolean whether it was for move only or not
284 'ArticleSave': before an article is saved
285 $article: the article (object) being saved
286 $user: the user (object) saving the article
287 $text: the new article text
288 $summary: the article summary (comment)
293 'ArticleSaveComplete': after an article is saved
294 $article: the article (object) saved
295 $user: the user (object) who saved the article
296 $text: the new article text
297 $summary: the article summary (comment)
302 'ArticleUndeleted': When one or more revisions of an article are restored
303 $title: Title corresponding to the article restored
304 $create: Whether or not the restoration caused the page to be created
305 (i.e. it didn't exist before)
307 'ArticleViewHeader': Before the parser cache is about to be tried for article viewing.
308 &$pcache: whether to try the parser cache or not
309 &$outputDone: whether the output for this page finished or not
311 'AuthPluginSetup': update or replace authentication plugin object ($wgAuth)
312 Gives a chance for an extension to set it programattically to a variable class.
313 &$auth: the $wgAuth object, probably a stub
315 'AutoAuthenticate': called to authenticate users on external/environmental means
316 $user: writes user object to this parameter
318 'BadImage': When checking against the bad image list
319 $name: Image name being checked
320 &$bad: Whether or not the image is "bad"
322 Change $bad and return false to override. If an image is "bad", it is not
323 rendered inline in wiki pages or galleries in category pages.
325 'BeforeGalleryFindFile': before an image is fetched for a gallery
326 &$gallery,: the gallery object
327 &$nt: the image title
328 &$time: image timestamp
330 'BeforeParserFetchTemplateAndtitle': before a template is fetched by Parser
331 &$parser: Parser object
332 &$title: title of the template
333 &$skip: skip this template and link it?
334 &$id: the id of the revision being parsed
336 'BeforeParserMakeImageLinkObj': before an image is rendered by Parser
337 &$parser: Parser object
338 &$nt: the image title
339 &$skip: skip this image and link it?
340 &$time: the image timestamp
342 'BeforeParserrenderImageGallery': before an image gallery is rendered by Parser
343 &$parser: Parser object
344 &$ig: ImageGallery object
346 'BlockIp': before an IP address or user is blocked
347 $block: the Block object about to be saved
348 $user: the user _doing_ the block (not the one being blocked)
350 'BlockIpComplete': after an IP address or user is blocked
351 $block: the Block object that was saved
352 $user: the user who did the block (not the one being blocked)
354 'BookInformation': Before information output on Special:Booksources
355 $isbn: ISBN to show information for
356 $output: OutputPage object in use
358 'CustomEditor': When invoking the page editor
359 $article: Article being edited
360 $user: User performing the edit
362 Return true to allow the normal editor to be used, or false
363 if implementing a custom editor, e.g. for a special namespace,
366 'DiffViewHeader': called before diff display
367 $diff: DifferenceEngine object that's calling
368 $oldRev: Revision object of the "old" revision (may be null/invalid)
369 $newRev: Revision object of the "new" revision
371 'EditPage::attemptSave': called before an article is
372 saved, that is before insertNewArticle() is called
373 &$editpage_Obj: the current EditPage object
375 'EditFormPreloadText': Allows population of the edit form when creating new pages
376 &$text: Text to preload with
377 &$title: Title object representing the page being created
379 'EditPage::showEditForm:fields': allows injection of form field into edit form
380 &$editor: the EditPage instance for reference
381 &$out: an OutputPage instance to write to
382 return value is ignored (should always return true)
384 'EditFilter': Perform checks on an edit
385 $editor: Edit form (see includes/EditPage.php)
386 $text: Contents of the edit box
387 $section: Section being edited
388 &$error: Error message to return
390 Return false to halt editing; you'll need to handle error messages, etc. yourself.
391 Alternatively, modifying $error and returning true will cause the contents of $error
392 to be echoed at the top of the edit form as wikitext. Return true without altering
393 $error to allow the edit to proceed.
395 'EditSectionLink': Override the return value of Linker::editSectionLink()
396 $skin: Skin rendering the UI
397 $title: Title being linked to
398 $section: Section to link to
400 $result: Result (alter this to override the generated links)
402 'EditSectionLinkForOther': Override the return value of Linker::editSectionLinkForOther()
403 $skin: Skin rendering the UI
404 $title: Title being linked to
405 $section: Section to link to
406 $hint: Anchor title/tooltip attributes
408 $result: Result (alter this to override the generated links)
410 'EmailConfirmed': When checking that the user's email address is "confirmed"
411 $user: User being checked
412 $confirmed: Whether or not the email address is confirmed
413 This runs before the other checks, such as anonymity and the real check; return
414 true to allow those checks to occur, and false if checking is done.
416 'EmailUser': before sending email from one user to another
417 $to: address of receiving user
418 $from: address of sending user
419 $subject: subject of the mail
420 $text: text of the mail
422 'EmailUserComplete': after sending email from one user to another
423 $to: address of receiving user
424 $from: address of sending user
425 $subject: subject of the mail
426 $text: text of the mail
428 'FetchChangesList': When fetching the ChangesList derivative for a particular user
429 &$user: User the list is being fetched for
430 &$skin: Skin object to be used with the list
431 &$list: List object (defaults to NULL, change it to an object instance and return
432 false override the list derivative used)
434 'FileUpload': When a file upload occurs
435 $file : Image object representing the file that was uploaded
437 'GetInternalURL': modify fully-qualified URLs used for squid cache purging
438 $title: Title object of page
439 $url: string value as output (out parameter, can modify)
440 $query: query options passed to Title::getInternalURL()
442 'GetLocalURL': modify local URLs as output into page links
443 $title: Title object of page
444 $url: string value as output (out parameter, can modify)
445 $query: query options passed to Title::getLocalURL()
447 'GetFullURL': modify fully-qualified URLs used in redirects/export/offsite data
448 $title: Title object of page
449 $url: string value as output (out parameter, can modify)
450 $query: query options passed to Title::getFullURL()
452 'ImageOpenShowImageInlineBefore': Call potential extension just before showing the image on an image page
453 $imagePage: ImagePage object ($this)
456 'InternalParseBeforeLinks': during Parser's internalParse method before links but
457 after noinclude/includeonly/onlyinclude and other processing.
458 &$this: Parser object
459 &$text: string containing partially parsed text
460 &$this->mStripState: Parser's internal StripState object
462 'LoginAuthenticateAudit': a login attempt for a valid user account either succeeded or failed.
463 No return data is accepted; this hook is for auditing only.
464 $user: the User object being authenticated against
465 $password: the password being submitted and found wanting
466 $retval: a LoginForm class constant with authenticateUserData() return value (SUCCESS, WRONG_PASS, etc)
468 'LogPageValidTypes': action being logged. DEPRECATED: Use $wgLogTypes
469 &$type: array of strings
471 'LogPageLogName': name of the logging page(s). DEPRECATED: Use $wgLogNames
472 &$typeText: array of strings
474 'LogPageLogHeader': strings used by wfMsg as a header. DEPRECATED: Use $wgLogHeaders
475 &$headerText: array of strings
477 'LogPageActionText': strings used by wfMsg as a header. DEPRECATED: Use $wgLogActions
478 &$actionText: array of strings
480 'MarkPatrolled': before an edit is marked patrolled
481 $rcid: ID of the revision to be marked patrolled
482 $user: the user (object) marking the revision as patrolled
483 $wcOnlySysopsCanPatrol: config setting indicating whether the user
484 needs to be a sysop in order to mark an edit patrolled
486 'MarkPatrolledComplete': after an edit is marked patrolled
487 $rcid: ID of the revision marked as patrolled
488 $user: user (object) who marked the edit patrolled
489 $wcOnlySysopsCanPatrol: config setting indicating whether the user
490 must be a sysop to patrol the edit
492 'MathAfterTexvc': after texvc is executed when rendering mathematics
493 $mathRenderer: instance of MathRenderer
494 $errmsg: error message, in HTML (string). Nonempty indicates failure
495 of rendering the formula
497 'OutputPageBeforeHTML': a page has been processed by the parser and
498 the resulting HTML is about to be displayed.
499 $parserOutput: the parserOutput (object) that corresponds to the page
500 $text: the text that will be displayed, in HTML (string)
502 'PageHistoryBeforeList': When a history page list is about to be constructed.
503 $article: the article that the history is loading for
505 'PageHistoryLineEnding' : right before the end <li> is added to a history line
506 $row: the revision row for this line
507 $s: the string representing this parsed line
509 'PageRenderingHash': alter the parser cache option hash key
510 A parser extension which depends on user options should install
511 this hook and append its values to the key.
512 $hash: reference to a hash key string which can be modified
514 'ParserTestTables': alter the list of tables to duplicate when parser tests
515 are run. Use when page save hooks require the presence of custom tables
516 to ensure that tests continue to run properly.
517 &$tables: array of table names
519 'PersonalUrls': Alter the user-specific navigation links (e.g. "my page,
520 my talk page, my contributions" etc).
522 &$personal_urls: Array of link specifiers (see SkinTemplate.php)
523 &$title: Title object representing the current page
525 'PingLimiter': Allows extensions to override the results of User::pingLimiter()
526 &$user : User performing the action
527 $action : Action being performed
528 &$result : Whether or not the action should be prevented
529 Change $result and return false to give a definitive answer, otherwise
530 the built-in rate limiting checks are used, if enabled.
532 'PreferencesUserInformationPanel': Add HTML bits to user information list in preferences form
533 $form : PreferencesForm object
534 &$html : HTML to append to
536 'RawPageViewBeforeOutput': Right before the text is blown out in action=raw
537 &$obj: RawPage object
538 &$text: The text that's going to be the output
540 'SearchUpdate': Prior to search update completion
542 $namespace : Page namespace
544 $text : Current text being indexed
546 'SiteNoticeBefore': Before the sitenotice/anonnotice is composed
547 &$siteNotice: HTML returned as the sitenotice
548 Return true to allow the normal method of notice selection/rendering to work,
549 or change the value of $siteNotice and return false to alter it.
551 'SiteNoticeAfter': After the sitenotice/anonnotice is composed
552 &$siteNotice: HTML sitenotice
553 Alter the contents of $siteNotice to add to/alter the sitenotice/anonnotice.
555 'SkinTemplateOutputPageBeforeExec': Before SkinTemplate::outputPage() starts page output
556 &$sktemplate: SkinTemplate object
557 &$tpl: Template engine object
559 'TitleLinkUpdatesAfterCompletion': after Linker->doUpdate() is called
560 &$title: title of the updated page
562 'TitleMoveComplete': after moving an article (title)
565 $user: user who did the move
566 $pageid: database ID of the page that's been moved
567 $redirid: database ID of the created redirect
569 'UnknownAction': An unknown "action" has occured (useful for defining
572 $article: article "acted on"
574 'UnwatchArticle': before a watch is removed from an article
576 $article: article object to be removed
578 'UnwatchArticle': after a watch is removed from an article
579 $user: user that was watching
580 $article: article object removed
582 'UploadForm:initial': before the upload form is generated
583 $form: UploadForm object
584 You might set the member-variables $uploadFormTextTop and
585 $uploadFormTextAfterSummary to inject text (HTML) either before
586 or after the editform.
588 'UploadForm:BeforeProcessing': at the beginning of processUpload()
589 $form: UploadForm object
590 Lets you poke at member variables like $mUploadDescription before the
593 'UploadVerification': additional chances to reject an uploaded file
594 string $saveName: destination file name
595 string $tempName: filesystem path to the temporary file for checks
596 string &$error: output: HTML error to show if upload canceled by returning false
598 'UploadComplete': Upon completion of a file upload
599 $image: Image object representing the file that was uploaded
601 'UserCan': To interrupt/advise the "user can do X to Y article" check
602 $title: Title object being checked against
603 $user : Current user object
604 $action: Action being checked
605 $result: Pointer to result returned if hook returns false. If null is returned,
606 UserCan checks are continued by internal code
608 'UserCreateForm': change to manipulate the login form
609 $template: SimpleTemplate instance for the form
611 'UserLoginComplete': after a user has logged in
612 $user: the user object that was created on login
614 'UserLoginForm': change to manipulate the login form
615 $template: SimpleTemplate instance for the form
617 'UserLogout': before a user logs out
618 $user: the user object that is about to be logged out
620 'UserLogoutComplete': after a user has logged out
621 $user: the user object _after_ logout (won't have name, ID, etc.)
623 'UserRights': After a user's group memberships are changed
624 $user : User object that was changed
625 $add : Array of strings corresponding to groups added
626 $remove: Array of strings corresponding to groups removed
628 'WatchArticle': before a watch is added to an article
629 $user: user that will watch
630 $article: article object to be watched
632 'WatchArticleComplete': after a watch is added to an article
633 $user: user that watched
634 $article: article object watched
636 'UnwatchArticleComplete': after a watch is removed from an article
637 $user: user that watched
638 $article: article object that was watched
640 'CategoryPageView': before viewing a categorypage in CategoryPage::view
641 $catpage: CategoryPage instance
643 'SkinTemplateContentActions': after building the $content_action array right
644 before returning it, see Content_action.php in
645 the extensions/examples/ directory
646 ( http://svn.wikimedia.org/viewvc/mediawiki/trunk/extensions/examples/ )
647 for a demonstration of how to use this hook.
648 $content_actions: The array of content actions
650 'BeforePageDisplay': Called just before outputting a page (all kinds of,
651 articles, special, history, preview, diff, edit, ...)
652 Can be used to set custom CSS/JS
653 $out: OutputPage object
655 'AjaxAddScript': Called in output page just before the initialisation
656 of the javascript ajax engine. The hook is only called when ajax
657 is enabled ( $wgUseAjax = true; ).
659 More hooks might be available but undocumented, you can execute
660 ./maintenance/findhooks.php to find hidden one.