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 $query: query options passed to Title::getFullURL()
406 'InternalParseBeforeLinks': during Parser's internalParse method before links but
407 after noinclude/includeonly/onlyinclude and other processing.
408 &$this: Parser object
409 &$text: string containing partially parsed text
410 &$this->mStripState: Parser's internal StripState object
412 'LoginAuthenticateAudit': a login attempt for a valid user account either succeeded or failed.
413 No return data is accepted; this hook is for auditing only.
414 $user: the User object being authenticated against
415 $password: the password being submitted and found wanting
416 $retval: a LoginForm class constant with authenticateUserData() return value (SUCCESS, WRONG_PASS, etc)
418 'LogPageValidTypes': action being logged. DEPRECATED: Use $wgLogTypes
419 &$type: array of strings
421 'LogPageLogName': name of the logging page(s). DEPRECATED: Use $wgLogNames
422 &$typeText: array of strings
424 'LogPageLogHeader': strings used by wfMsg as a header. DEPRECATED: Use $wgLogHeaders
425 &$headerText: array of strings
427 'LogPageActionText': strings used by wfMsg as a header. DEPRECATED: Use $wgLogActions
428 &$actionText: array of strings
430 'MarkPatrolled': before an edit is marked patrolled
431 $rcid: ID of the revision to be marked patrolled
432 $user: the user (object) marking the revision as patrolled
433 $wcOnlySysopsCanPatrol: config setting indicating whether the user
434 needs to be a sysop in order to mark an edit patrolled
436 'MarkPatrolledComplete': after an edit is marked patrolled
437 $rcid: ID of the revision marked as patrolled
438 $user: user (object) who marked the edit patrolled
439 $wcOnlySysopsCanPatrol: config setting indicating whether the user
440 must be a sysop to patrol the edit
442 'MathAfterTexvc': after texvc is executed when rendering mathematics
443 $mathRenderer: instance of MathRenderer
444 $errmsg: error message, in HTML (string). Nonempty indicates failure
445 of rendering the formula
447 'OutputPageBeforeHTML': a page has been processed by the parser and
448 the resulting HTML is about to be displayed.
449 $parserOutput: the parserOutput (object) that corresponds to the page
450 $text: the text that will be displayed, in HTML (string)
452 'PageHistoryBeforeList': When a history page list is about to be constructed.
453 $article: the article that the history is loading for
455 'PageHistoryLineEnding' : right before the end <li> is added to a history line
456 $row: the revision row for this line
457 $s: the string representing this parsed line
459 'PageRenderingHash': alter the parser cache option hash key
460 A parser extension which depends on user options should install
461 this hook and append its values to the key.
462 $hash: reference to a hash key string which can be modified
464 'ParserTestTables': alter the list of tables to duplicate when parser tests
465 are run. Use when page save hooks require the presence of custom tables
466 to ensure that tests continue to run properly.
467 &$tables: array of table names
469 'PersonalUrls': Alter the user-specific navigation links (e.g. "my page,
470 my talk page, my contributions" etc).
472 &$personal_urls: Array of link specifiers (see SkinTemplate.php)
473 &$title: Title object representing the current page
475 'PingLimiter': Allows extensions to override the results of User::pingLimiter()
476 &$user : User performing the action
477 $action : Action being performed
478 &$result : Whether or not the action should be prevented
479 Change $result and return false to give a definitive answer, otherwise
480 the built-in rate limiting checks are used, if enabled.
482 'PreferencesUserInformationPanel': Add HTML bits to user information list in preferences form
483 $form : PreferencesForm object
484 &$html : HTML to append to
486 'RawPageViewBeforeOutput': Right before the text is blown out in action=raw
487 &$obj: RawPage object
488 &$text: The text that's going to be the output
490 'SearchUpdate': Prior to search update completion
492 $namespace : Page namespace
494 $text : Current text being indexed
496 'SiteNoticeBefore': Before the sitenotice/anonnotice is composed
497 &$siteNotice: HTML returned as the sitenotice
498 Return true to allow the normal method of notice selection/rendering to work,
499 or change the value of $siteNotice and return false to alter it.
501 'SiteNoticeAfter': After the sitenotice/anonnotice is composed
502 &$siteNotice: HTML sitenotice
503 Alter the contents of $siteNotice to add to/alter the sitenotice/anonnotice.
505 'SkinTemplateOutputPageBeforeExec': Before SkinTemplate::outputPage() starts page output
506 &$sktemplate: SkinTemplate object
507 &$tpl: Template engine object
509 'TitleMoveComplete': after moving an article (title)
512 $user: user who did the move
513 $pageid: database ID of the page that's been moved
514 $redirid: database ID of the created redirect
516 'UnknownAction': An unknown "action" has occured (useful for defining
519 $article: article "acted on"
521 'UnwatchArticle': before a watch is removed from an article
523 $article: article object to be removed
525 'UnwatchArticle': after a watch is removed from an article
526 $user: user that was watching
527 $article: article object removed
529 'UploadForm:initial': before the upload form is generated
530 $form: UploadForm object
531 You might set the member-variables $uploadFormTextTop and
532 $uploadFormTextAfterSummary to inject text (HTML) either before
533 or after the editform.
535 'UploadForm:BeforeProcessing': at the beginning of processUpload()
536 $form: UploadForm object
537 Lets you poke at member variables like $mUploadDescription before the
540 'UploadVerification': additional chances to reject an uploaded file
541 string $saveName: destination file name
542 string $tempName: filesystem path to the temporary file for checks
543 string &$error: output: HTML error to show if upload canceled by returning false
545 'UploadComplete': Upon completion of a file upload
546 $image: Image object representing the file that was uploaded
548 'UserCan': To interrupt/advise the "user can do X to Y article" check
549 $title: Title object being checked against
550 $user : Current user object
551 $action: Action being checked
552 $result: Pointer to result returned if hook returns false. If null is returned,
553 UserCan checks are continued by internal code
555 'UserCreateForm': change to manipulate the login form
556 $template: SimpleTemplate instance for the form
558 'UserLoginComplete': after a user has logged in
559 $user: the user object that was created on login
561 'UserLoginForm': change to manipulate the login form
562 $template: SimpleTemplate instance for the form
564 'UserLogout': before a user logs out
565 $user: the user object that is about to be logged out
567 'UserLogoutComplete': after a user has logged out
568 $user: the user object _after_ logout (won't have name, ID, etc.)
570 'UserRights': After a user's group memberships are changed
571 $user : User object that was changed
572 $add : Array of strings corresponding to groups added
573 $remove: Array of strings corresponding to groups removed
575 'WatchArticle': before a watch is added to an article
576 $user: user that will watch
577 $article: article object to be watched
579 'WatchArticleComplete': after a watch is added to an article
580 $user: user that watched
581 $article: article object watched
583 'UnwatchArticleComplete': after a watch is removed from an article
584 $user: user that watched
585 $article: article object that was watched
587 'CategoryPageView': before viewing a categorypage in CategoryPage::view
588 $catpage: CategoryPage instance
590 'SkinTemplateContentActions': after building the $content_action array right
591 before returning it, see Content_action.php in
592 the extensions/examples/ directory
593 ( http://svn.wikimedia.org/viewvc/mediawiki/trunk/extensions/examples/ )
594 for a demonstration of how to use this hook.
595 $content_actions: The array of content actions
597 'BeforePageDisplay': Called just before outputting a page (all kinds of,
598 articles, special, history, preview, diff, edit, ...)
599 Can be used to set custom CSS/JS
600 $out: OutputPage object
602 'AjaxAddScript': Called in output page just before the initialisation
603 of the javascript ajax engine. The hook is only called when ajax
604 is enabled ( $wgUseAjax = true; ).
606 More hooks might be available but undocumented, you can execute
607 ./maintenance/findhooks.php to find hidden one.