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));
223 wfRunHooks() returns true if the calling function should continue
224 processing (the hooks ran OK, or there are no hooks to run), or false
225 if it shouldn't (an error occurred, or one of the hooks handled the
226 action already). Checking the return value matters more for "before"
227 hooks than for "complete" hooks.
229 Note that hook parameters are passed in an array; this is a necessary
230 inconvenience to make it possible to pass reference values (that can
231 be changed) into the hook code. Also note that earlier versions of
232 wfRunHooks took a variable number of arguments; the array() calling
233 protocol came about after MediaWiki 1.4rc1.
235 ==Events and parameters==
237 This is a list of known events and parameters; please add to it if
238 you're going to add events to the MediaWiki code.
240 'AbortLogin': Return false to cancel account login.
241 $user: the User object being authenticated against
242 $password: the password being submitted, not yet checked for validity
243 &$retval: a LoginForm class constant to return from authenticateUserData();
244 default is LoginForm::ABORTED. Note that the client may be using
245 a machine API rather than the HTML user interface.
247 'AbortNewAccount': Return false to cancel account creation.
248 $user: the User object about to be created (read-only, incomplete)
249 $message: out parameter: error message to display on abort
251 'AddNewAccount': after a user account is created
252 $user: the User object that was created. (Parameter added in 1.7)
254 'ArticleDelete': before an article is deleted
255 $article: the article (object) being deleted
256 $user: the user (object) deleting the article
257 $reason: the reason (string) the article is being deleted
259 'ArticleDeleteComplete': after an article is deleted
260 $article: the article that was deleted
261 $user: the user that deleted the article
262 $reason: the reason the article was deleted
264 'ArticleProtect': before an article is protected
265 $article: the article being protected
266 $user: the user doing the protection
267 $protect: boolean whether this is a protect or an unprotect
268 $reason: Reason for protect
269 $moveonly: boolean whether this is for move only or not
271 'ArticleProtectComplete': after an article is protected
272 $article: the article that was protected
273 $user: the user who did the protection
274 $protect: boolean whether it was a protect or an unprotect
275 $reason: Reason for protect
276 $moveonly: boolean whether it was for move only or not
278 'ArticleSave': before an article is saved
279 $article: the article (object) being saved
280 $user: the user (object) saving the article
281 $text: the new article text
282 $summary: the article summary (comment)
287 'ArticleSaveComplete': after an article is saved
288 $article: the article (object) saved
289 $user: the user (object) who saved the article
290 $text: the new article text
291 $summary: the article summary (comment)
296 'ArticleUndeleted': When one or more revisions of an article are restored
297 $title: Title corresponding to the article restored
298 $create: Whether or not the restoration caused the page to be created
299 (i.e. it didn't exist before)
301 'AuthPluginSetup': update or replace authentication plugin object ($wgAuth)
302 Gives a chance for an extension to set it programattically to a variable class.
303 &$auth: the $wgAuth object, probably a stub
305 'AutoAuthenticate': called to authenticate users on external/environmental means
306 $user: writes user object to this parameter
308 'BadImage': When checking against the bad image list
309 $name: Image name being checked
310 &$bad: Whether or not the image is "bad"
312 Change $bad and return false to override. If an image is "bad", it is not
313 rendered inline in wiki pages or galleries in category pages.
315 'BlockIp': before an IP address or user is blocked
316 $block: the Block object about to be saved
317 $user: the user _doing_ the block (not the one being blocked)
319 'BlockIpComplete': after an IP address or user is blocked
320 $block: the Block object that was saved
321 $user: the user who did the block (not the one being blocked)
323 'BookInformation': Before information output on Special:Booksources
324 $isbn: ISBN to show information for
325 $output: OutputPage object in use
327 'CustomEditor': When invoking the page editor
328 $article: Article being edited
329 $user: User performing the edit
331 Return true to allow the normal editor to be used, or false
332 if implementing a custom editor, e.g. for a special namespace,
335 'DiffViewHeader': called before diff display
336 $diff: DifferenceEngine object that's calling
337 $oldRev: Revision object of the "old" revision (may be null/invalid)
338 $newRev: Revision object of the "new" revision
340 'EditPage::attemptSave': called before an article is
341 saved, that is before insertNewArticle() is called
342 &$editpage_Obj: the current EditPage object
344 'EditFormPreloadText': Allows population of the edit form when creating new pages
345 &$text: Text to preload with
346 &$title: Title object representing the page being created
348 'EditPage::showEditForm:fields': allows injection of form field into edit form
349 &$editor: the EditPage instance for reference
350 &$out: an OutputPage instance to write to
351 return value is ignored (should always return true)
353 'EditFilter': Perform checks on an edit
354 $editor: Edit form (see includes/EditPage.php)
355 $text: Contents of the edit box
356 $section: Section being edited
357 &$error: Error message to return
359 Return false to halt editing; you'll need to handle error messages, etc. yourself.
360 Alternatively, modifying $error and returning true will cause the contents of $error
361 to be echoed at the top of the edit form as wikitext. Return true without altering
362 $error to allow the edit to proceed.
364 'EmailConfirmed': When checking that the user's email address is "confirmed"
365 $user: User being checked
366 $confirmed: Whether or not the email address is confirmed
367 This runs before the other checks, such as anonymity and the real check; return
368 true to allow those checks to occur, and false if checking is done.
370 'EmailUser': before sending email from one user to another
371 $to: address of receiving user
372 $from: address of sending user
373 $subject: subject of the mail
374 $text: text of the mail
376 'EmailUserComplete': after sending email from one user to another
377 $to: address of receiving user
378 $from: address of sending user
379 $subject: subject of the mail
380 $text: text of the mail
382 'FetchChangesList': When fetching the ChangesList derivative for a particular user
383 &$user: User the list is being fetched for
384 &$skin: Skin object to be used with the list
385 &$list: List object (defaults to NULL, change it to an object instance and return
386 false override the list derivative used)
388 'FileUpload': When a file upload occurs
389 $file : Image object representing the file that was uploaded
391 'GetInternalURL': modify fully-qualified URLs used for squid cache purging
392 $title: Title object of page
393 $url: string value as output (out parameter, can modify)
394 $query: query options passed to Title::getInternalURL()
396 'GetLocalURL': modify local URLs as output into page links
397 $title: Title object of page
398 $url: string value as output (out parameter, can modify)
399 $query: query options passed to Title::getLocalURL()
401 'GetFullURL': modify fully-qualified URLs used in redirects/export/offsite data
402 $title: Title object of page
403 $url: string value as output (out parameter, can modify)
404 $query: query options passed to Title::getFullURL()
406 'ImageOpenShowImageInlineBefore': Call potential extension just before showing the image on an image page
407 $imagePage: ImagePage object ($this)
410 'InternalParseBeforeLinks': during Parser's internalParse method before links but
411 after noinclude/includeonly/onlyinclude and other processing.
412 &$this: Parser object
413 &$text: string containing partially parsed text
414 &$this->mStripState: Parser's internal StripState object
416 'LoginAuthenticateAudit': a login attempt for a valid user account either succeeded or failed.
417 No return data is accepted; this hook is for auditing only.
418 $user: the User object being authenticated against
419 $password: the password being submitted and found wanting
420 $retval: a LoginForm class constant with authenticateUserData() return value (SUCCESS, WRONG_PASS, etc)
422 'LogPageValidTypes': action being logged. DEPRECATED: Use $wgLogTypes
423 &$type: array of strings
425 'LogPageLogName': name of the logging page(s). DEPRECATED: Use $wgLogNames
426 &$typeText: array of strings
428 'LogPageLogHeader': strings used by wfMsg as a header. DEPRECATED: Use $wgLogHeaders
429 &$headerText: array of strings
431 'LogPageActionText': strings used by wfMsg as a header. DEPRECATED: Use $wgLogActions
432 &$actionText: array of strings
434 'MarkPatrolled': before an edit is marked patrolled
435 $rcid: ID of the revision to be marked patrolled
436 $user: the user (object) marking the revision as patrolled
437 $wcOnlySysopsCanPatrol: config setting indicating whether the user
438 needs to be a sysop in order to mark an edit patrolled
440 'MarkPatrolledComplete': after an edit is marked patrolled
441 $rcid: ID of the revision marked as patrolled
442 $user: user (object) who marked the edit patrolled
443 $wcOnlySysopsCanPatrol: config setting indicating whether the user
444 must be a sysop to patrol the edit
446 'MathAfterTexvc': after texvc is executed when rendering mathematics
447 $mathRenderer: instance of MathRenderer
448 $errmsg: error message, in HTML (string). Nonempty indicates failure
449 of rendering the formula
451 'OutputPageBeforeHTML': a page has been processed by the parser and
452 the resulting HTML is about to be displayed.
453 $parserOutput: the parserOutput (object) that corresponds to the page
454 $text: the text that will be displayed, in HTML (string)
456 'PageHistoryBeforeList': When a history page list is about to be constructed.
457 $article: the article that the history is loading for
459 'PageHistoryLineEnding' : right before the end <li> is added to a history line
460 $row: the revision row for this line
461 $s: the string representing this parsed line
463 'PageRenderingHash': alter the parser cache option hash key
464 A parser extension which depends on user options should install
465 this hook and append its values to the key.
466 $hash: reference to a hash key string which can be modified
468 'ParserTestTables': alter the list of tables to duplicate when parser tests
469 are run. Use when page save hooks require the presence of custom tables
470 to ensure that tests continue to run properly.
471 &$tables: array of table names
473 'PersonalUrls': Alter the user-specific navigation links (e.g. "my page,
474 my talk page, my contributions" etc).
476 &$personal_urls: Array of link specifiers (see SkinTemplate.php)
477 &$title: Title object representing the current page
479 'PingLimiter': Allows extensions to override the results of User::pingLimiter()
480 &$user : User performing the action
481 $action : Action being performed
482 &$result : Whether or not the action should be prevented
483 Change $result and return false to give a definitive answer, otherwise
484 the built-in rate limiting checks are used, if enabled.
486 'PreferencesUserInformationPanel': Add HTML bits to user information list in preferences form
487 $form : PreferencesForm object
488 &$html : HTML to append to
490 'RawPageViewBeforeOutput': Right before the text is blown out in action=raw
491 &$obj: RawPage object
492 &$text: The text that's going to be the output
494 'SearchUpdate': Prior to search update completion
496 $namespace : Page namespace
498 $text : Current text being indexed
500 'SiteNoticeBefore': Before the sitenotice/anonnotice is composed
501 &$siteNotice: HTML returned as the sitenotice
502 Return true to allow the normal method of notice selection/rendering to work,
503 or change the value of $siteNotice and return false to alter it.
505 'SiteNoticeAfter': After the sitenotice/anonnotice is composed
506 &$siteNotice: HTML sitenotice
507 Alter the contents of $siteNotice to add to/alter the sitenotice/anonnotice.
509 'SkinTemplateOutputPageBeforeExec': Before SkinTemplate::outputPage() starts page output
510 &$sktemplate: SkinTemplate object
511 &$tpl: Template engine object
513 'TitleMoveComplete': after moving an article (title)
516 $user: user who did the move
517 $pageid: database ID of the page that's been moved
518 $redirid: database ID of the created redirect
520 'UnknownAction': An unknown "action" has occured (useful for defining
523 $article: article "acted on"
525 'UnwatchArticle': before a watch is removed from an article
527 $article: article object to be removed
529 'UnwatchArticle': after a watch is removed from an article
530 $user: user that was watching
531 $article: article object removed
533 'UploadForm:initial': before the upload form is generated
534 $form: UploadForm object
535 You might set the member-variables $uploadFormTextTop and
536 $uploadFormTextAfterSummary to inject text (HTML) either before
537 or after the editform.
539 'UploadForm:BeforeProcessing': at the beginning of processUpload()
540 $form: UploadForm object
541 Lets you poke at member variables like $mUploadDescription before the
544 'UploadVerification': additional chances to reject an uploaded file
545 string $saveName: destination file name
546 string $tempName: filesystem path to the temporary file for checks
547 string &$error: output: HTML error to show if upload canceled by returning false
549 'UploadComplete': Upon completion of a file upload
550 $image: Image object representing the file that was uploaded
552 'UserCan': To interrupt/advise the "user can do X to Y article" check
553 $title: Title object being checked against
554 $user : Current user object
555 $action: Action being checked
556 $result: Pointer to result returned if hook returns false. If null is returned,
557 UserCan checks are continued by internal code
559 'UserCreateForm': change to manipulate the login form
560 $template: SimpleTemplate instance for the form
562 'UserLoginComplete': after a user has logged in
563 $user: the user object that was created on login
565 'UserLoginForm': change to manipulate the login form
566 $template: SimpleTemplate instance for the form
568 'UserLogout': before a user logs out
569 $user: the user object that is about to be logged out
571 'UserLogoutComplete': after a user has logged out
572 $user: the user object _after_ logout (won't have name, ID, etc.)
574 'UserRights': After a user's group memberships are changed
575 $user : User object that was changed
576 $add : Array of strings corresponding to groups added
577 $remove: Array of strings corresponding to groups removed
579 'WatchArticle': before a watch is added to an article
580 $user: user that will watch
581 $article: article object to be watched
583 'WatchArticleComplete': after a watch is added to an article
584 $user: user that watched
585 $article: article object watched
587 'UnwatchArticleComplete': after a watch is removed from an article
588 $user: user that watched
589 $article: article object that was watched
591 'CategoryPageView': before viewing a categorypage in CategoryPage::view
592 $catpage: CategoryPage instance
594 'SkinTemplateContentActions': after building the $content_action array right
595 before returning it, see Content_action.php in
596 the extensions/examples/ directory
597 ( http://svn.wikimedia.org/viewvc/mediawiki/trunk/extensions/examples/ )
598 for a demonstration of how to use this hook.
599 $content_actions: The array of content actions
601 'BeforePageDisplay': Called just before outputting a page (all kinds of,
602 articles, special, history, preview, diff, edit, ...)
603 Can be used to set custom CSS/JS
604 $out: OutputPage object
606 'AjaxAddScript': Called in output page just before the initialisation
607 of the javascript ajax engine. The hook is only called when ajax
608 is enabled ( $wgUseAjax = true; ).
610 More hooks might be available but undocumented, you can execute
611 ./maintenance/findhooks.php to find hidden one.