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 'AlternateEdit': before checking if an user can edit a page and
255 before showing the edit form ( EditPage::edit() ). This is triggered
257 $EditPage : the EditPage object
259 'ArticleDelete': before an article is deleted
260 $article: the article (object) being deleted
261 $user: the user (object) deleting the article
262 $reason: the reason (string) the article is being deleted
264 'ArticleDeleteComplete': after an article is deleted
265 $article: the article that was deleted
266 $user: the user that deleted the article
267 $reason: the reason the article was deleted
269 'ArticleProtect': before an article is protected
270 $article: the article being protected
271 $user: the user doing the protection
272 $protect: boolean whether this is a protect or an unprotect
273 $reason: Reason for protect
274 $moveonly: boolean whether this is for move only or not
276 'ArticleProtectComplete': after an article is protected
277 $article: the article that was protected
278 $user: the user who did the protection
279 $protect: boolean whether it was a protect or an unprotect
280 $reason: Reason for protect
281 $moveonly: boolean whether it was for move only or not
283 'ArticleSave': before an article is saved
284 $article: the article (object) being saved
285 $user: the user (object) saving the article
286 $text: the new article text
287 $summary: the article summary (comment)
292 'ArticleSaveComplete': after an article is saved
293 $article: the article (object) saved
294 $user: the user (object) who saved the article
295 $text: the new article text
296 $summary: the article summary (comment)
301 'ArticleUndeleted': When one or more revisions of an article are restored
302 $title: Title corresponding to the article restored
303 $create: Whether or not the restoration caused the page to be created
304 (i.e. it didn't exist before)
306 'ArticleViewHeader': Before the parser cache is about to be tried for article viewing.
307 &$pcache: whether to try the parser cache or not
308 &$outputDone: whether the output for this page finished or not
310 'AuthPluginSetup': update or replace authentication plugin object ($wgAuth)
311 Gives a chance for an extension to set it programattically to a variable class.
312 &$auth: the $wgAuth object, probably a stub
314 'AutoAuthenticate': called to authenticate users on external/environmental means
315 $user: writes user object to this parameter
317 'BadImage': When checking against the bad image list
318 $name: Image name being checked
319 &$bad: Whether or not the image is "bad"
321 Change $bad and return false to override. If an image is "bad", it is not
322 rendered inline in wiki pages or galleries in category pages.
324 'BeforeGalleryFindFile': before an image is fetched for a gallery
325 &$gallery,: the gallery object
326 &$nt: the image title
327 &$time: image timestamp
329 'BeforeParserFetchTemplateAndtitle': before a template is fetched by Parser
330 &$parser: Parser object
331 &$title: title of the template
332 &$skip: skip this template and link it?
333 &$id: the id of the revision being parsed
335 'BeforeParserMakeImageLinkObj': before an image is rendered by Parser
336 &$parser: Parser object
337 &$nt: the image title
338 &$skip: skip this image and link it?
339 &$time: the image timestamp
341 'BeforeParserrenderImageGallery': before an image gallery is rendered by Parser
342 &$parser: Parser object
343 &$ig: ImageGallery object
345 'BlockIp': before an IP address or user is blocked
346 $block: the Block object about to be saved
347 $user: the user _doing_ the block (not the one being blocked)
349 'BlockIpComplete': after an IP address or user is blocked
350 $block: the Block object that was saved
351 $user: the user who did the block (not the one being blocked)
353 'BookInformation': Before information output on Special:Booksources
354 $isbn: ISBN to show information for
355 $output: OutputPage object in use
357 'CustomEditor': When invoking the page editor
358 $article: Article being edited
359 $user: User performing the edit
361 Return true to allow the normal editor to be used, or false
362 if implementing a custom editor, e.g. for a special namespace,
365 'DiffViewHeader': called before diff display
366 $diff: DifferenceEngine object that's calling
367 $oldRev: Revision object of the "old" revision (may be null/invalid)
368 $newRev: Revision object of the "new" revision
370 'EditPage::attemptSave': called before an article is
371 saved, that is before insertNewArticle() is called
372 &$editpage_Obj: the current EditPage object
374 'EditFormPreloadText': Allows population of the edit form when creating new pages
375 &$text: Text to preload with
376 &$title: Title object representing the page being created
378 'EditPage::showEditForm:fields': allows injection of form field into edit form
379 &$editor: the EditPage instance for reference
380 &$out: an OutputPage instance to write to
381 return value is ignored (should always return true)
383 'EditFilter': Perform checks on an edit
384 $editor: Edit form (see includes/EditPage.php)
385 $text: Contents of the edit box
386 $section: Section being edited
387 &$error: Error message to return
389 Return false to halt editing; you'll need to handle error messages, etc. yourself.
390 Alternatively, modifying $error and returning true will cause the contents of $error
391 to be echoed at the top of the edit form as wikitext. Return true without altering
392 $error to allow the edit to proceed.
394 'EditSectionLink': Override the return value of Linker::editSectionLink()
395 $skin: Skin rendering the UI
396 $title: Title being linked to
397 $section: Section to link to
399 $result: Result (alter this to override the generated links)
401 'EditSectionLinkForOther': Override the return value of Linker::editSectionLinkForOther()
402 $skin: Skin rendering the UI
403 $title: Title being linked to
404 $section: Section to link to
405 $hint: Anchor title/tooltip attributes
407 $result: Result (alter this to override the generated links)
409 'EmailConfirmed': When checking that the user's email address is "confirmed"
410 $user: User being checked
411 $confirmed: Whether or not the email address is confirmed
412 This runs before the other checks, such as anonymity and the real check; return
413 true to allow those checks to occur, and false if checking is done.
415 'EmailUser': before sending email from one user to another
416 $to: address of receiving user
417 $from: address of sending user
418 $subject: subject of the mail
419 $text: text of the mail
421 'EmailUserComplete': after sending email from one user to another
422 $to: address of receiving user
423 $from: address of sending user
424 $subject: subject of the mail
425 $text: text of the mail
427 'FetchChangesList': When fetching the ChangesList derivative for a particular user
428 &$user: User the list is being fetched for
429 &$skin: Skin object to be used with the list
430 &$list: List object (defaults to NULL, change it to an object instance and return
431 false override the list derivative used)
433 'FileUpload': When a file upload occurs
434 $file : Image object representing the file that was uploaded
436 'GetInternalURL': modify fully-qualified URLs used for squid cache purging
437 $title: Title object of page
438 $url: string value as output (out parameter, can modify)
439 $query: query options passed to Title::getInternalURL()
441 'GetLocalURL': modify local URLs as output into page links
442 $title: Title object of page
443 $url: string value as output (out parameter, can modify)
444 $query: query options passed to Title::getLocalURL()
446 'GetFullURL': modify fully-qualified URLs used in redirects/export/offsite data
447 $title: Title object of page
448 $url: string value as output (out parameter, can modify)
449 $query: query options passed to Title::getFullURL()
451 'ImageOpenShowImageInlineBefore': Call potential extension just before showing the image on an image page
452 $imagePage: ImagePage object ($this)
455 'InternalParseBeforeLinks': during Parser's internalParse method before links but
456 after noinclude/includeonly/onlyinclude and other processing.
457 &$this: Parser object
458 &$text: string containing partially parsed text
459 &$this->mStripState: Parser's internal StripState object
461 'LoginAuthenticateAudit': a login attempt for a valid user account either succeeded or failed.
462 No return data is accepted; this hook is for auditing only.
463 $user: the User object being authenticated against
464 $password: the password being submitted and found wanting
465 $retval: a LoginForm class constant with authenticateUserData() return value (SUCCESS, WRONG_PASS, etc)
467 'LogPageValidTypes': action being logged. DEPRECATED: Use $wgLogTypes
468 &$type: array of strings
470 'LogPageLogName': name of the logging page(s). DEPRECATED: Use $wgLogNames
471 &$typeText: array of strings
473 'LogPageLogHeader': strings used by wfMsg as a header. DEPRECATED: Use $wgLogHeaders
474 &$headerText: array of strings
476 'LogPageActionText': strings used by wfMsg as a header. DEPRECATED: Use $wgLogActions
477 &$actionText: array of strings
479 'MarkPatrolled': before an edit is marked patrolled
480 $rcid: ID of the revision to be marked patrolled
481 $user: the user (object) marking the revision as patrolled
482 $wcOnlySysopsCanPatrol: config setting indicating whether the user
483 needs to be a sysop in order to mark an edit patrolled
485 'MarkPatrolledComplete': after an edit is marked patrolled
486 $rcid: ID of the revision marked as patrolled
487 $user: user (object) who marked the edit patrolled
488 $wcOnlySysopsCanPatrol: config setting indicating whether the user
489 must be a sysop to patrol the edit
491 'MathAfterTexvc': after texvc is executed when rendering mathematics
492 $mathRenderer: instance of MathRenderer
493 $errmsg: error message, in HTML (string). Nonempty indicates failure
494 of rendering the formula
496 'OutputPageBeforeHTML': a page has been processed by the parser and
497 the resulting HTML is about to be displayed.
498 $parserOutput: the parserOutput (object) that corresponds to the page
499 $text: the text that will be displayed, in HTML (string)
501 'PageHistoryBeforeList': When a history page list is about to be constructed.
502 $article: the article that the history is loading for
504 'PageHistoryLineEnding' : right before the end <li> is added to a history line
505 $row: the revision row for this line
506 $s: the string representing this parsed line
508 'PageRenderingHash': alter the parser cache option hash key
509 A parser extension which depends on user options should install
510 this hook and append its values to the key.
511 $hash: reference to a hash key string which can be modified
513 'ParserTestTables': alter the list of tables to duplicate when parser tests
514 are run. Use when page save hooks require the presence of custom tables
515 to ensure that tests continue to run properly.
516 &$tables: array of table names
518 'PersonalUrls': Alter the user-specific navigation links (e.g. "my page,
519 my talk page, my contributions" etc).
521 &$personal_urls: Array of link specifiers (see SkinTemplate.php)
522 &$title: Title object representing the current page
524 'PingLimiter': Allows extensions to override the results of User::pingLimiter()
525 &$user : User performing the action
526 $action : Action being performed
527 &$result : Whether or not the action should be prevented
528 Change $result and return false to give a definitive answer, otherwise
529 the built-in rate limiting checks are used, if enabled.
531 'PreferencesUserInformationPanel': Add HTML bits to user information list in preferences form
532 $form : PreferencesForm object
533 &$html : HTML to append to
535 'RawPageViewBeforeOutput': Right before the text is blown out in action=raw
536 &$obj: RawPage object
537 &$text: The text that's going to be the output
539 'SearchUpdate': Prior to search update completion
541 $namespace : Page namespace
543 $text : Current text being indexed
545 'SiteNoticeBefore': Before the sitenotice/anonnotice is composed
546 &$siteNotice: HTML returned as the sitenotice
547 Return true to allow the normal method of notice selection/rendering to work,
548 or change the value of $siteNotice and return false to alter it.
550 'SiteNoticeAfter': After the sitenotice/anonnotice is composed
551 &$siteNotice: HTML sitenotice
552 Alter the contents of $siteNotice to add to/alter the sitenotice/anonnotice.
554 'SkinTemplateOutputPageBeforeExec': Before SkinTemplate::outputPage() starts page output
555 &$sktemplate: SkinTemplate object
556 &$tpl: Template engine object
558 'TitleLinkUpdatesAfterCompletion': after Linker->doUpdate() is called
559 &$title: title of the updated page
561 'TitleMoveComplete': after moving an article (title)
564 $user: user who did the move
565 $pageid: database ID of the page that's been moved
566 $redirid: database ID of the created redirect
568 'UnknownAction': An unknown "action" has occured (useful for defining
571 $article: article "acted on"
573 'UnwatchArticle': before a watch is removed from an article
575 $article: article object to be removed
577 'UnwatchArticle': after a watch is removed from an article
578 $user: user that was watching
579 $article: article object removed
581 'UploadForm:initial': before the upload form is generated
582 $form: UploadForm object
583 You might set the member-variables $uploadFormTextTop and
584 $uploadFormTextAfterSummary to inject text (HTML) either before
585 or after the editform.
587 'UploadForm:BeforeProcessing': at the beginning of processUpload()
588 $form: UploadForm object
589 Lets you poke at member variables like $mUploadDescription before the
592 'UploadVerification': additional chances to reject an uploaded file
593 string $saveName: destination file name
594 string $tempName: filesystem path to the temporary file for checks
595 string &$error: output: HTML error to show if upload canceled by returning false
597 'UploadComplete': Upon completion of a file upload
598 $image: Image object representing the file that was uploaded
600 'UserCan': To interrupt/advise the "user can do X to Y article" check
601 $title: Title object being checked against
602 $user : Current user object
603 $action: Action being checked
604 $result: Pointer to result returned if hook returns false. If null is returned,
605 UserCan checks are continued by internal code
607 'UserCreateForm': change to manipulate the login form
608 $template: SimpleTemplate instance for the form
610 'UserLoginComplete': after a user has logged in
611 $user: the user object that was created on login
613 'UserLoginForm': change to manipulate the login form
614 $template: SimpleTemplate instance for the form
616 'UserLogout': before a user logs out
617 $user: the user object that is about to be logged out
619 'UserLogoutComplete': after a user has logged out
620 $user: the user object _after_ logout (won't have name, ID, etc.)
622 'UserRights': After a user's group memberships are changed
623 $user : User object that was changed
624 $add : Array of strings corresponding to groups added
625 $remove: Array of strings corresponding to groups removed
627 'WatchArticle': before a watch is added to an article
628 $user: user that will watch
629 $article: article object to be watched
631 'WatchArticleComplete': after a watch is added to an article
632 $user: user that watched
633 $article: article object watched
635 'UnwatchArticleComplete': after a watch is removed from an article
636 $user: user that watched
637 $article: article object that was watched
639 'CategoryPageView': before viewing a categorypage in CategoryPage::view
640 $catpage: CategoryPage instance
642 'SkinTemplateContentActions': after building the $content_action array right
643 before returning it, see Content_action.php in
644 the extensions/examples/ directory
645 ( http://svn.wikimedia.org/viewvc/mediawiki/trunk/extensions/examples/ )
646 for a demonstration of how to use this hook.
647 $content_actions: The array of content actions
649 'BeforePageDisplay': Called just before outputting a page (all kinds of,
650 articles, special, history, preview, diff, edit, ...)
651 Can be used to set custom CSS/JS
652 $out: OutputPage object
654 'AjaxAddScript': Called in output page just before the initialisation
655 of the javascript ajax engine. The hook is only called when ajax
656 is enabled ( $wgUseAjax = true; ).
658 More hooks might be available but undocumented, you can execute
659 ./maintenance/findhooks.php to find hidden one.