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 'AbortNewAccount': Return false to cancel account creation.
241 $user: the User object about to be created (read-only, incomplete)
242 $message: out parameter: error message to display on abort
244 'AddNewAccount': after a user account is created
245 $user: the User object that was created. (Parameter added in 1.7)
247 'ArticleDelete': before an article is deleted
248 $article: the article (object) being deleted
249 $user: the user (object) deleting the article
250 $reason: the reason (string) the article is being deleted
252 'ArticleDeleteComplete': after an article is deleted
253 $article: the article that was deleted
254 $user: the user that deleted the article
255 $reason: the reason the article was deleted
257 'ArticleProtect': before an article is protected
258 $article: the article being protected
259 $user: the user doing the protection
260 $protect: boolean whether this is a protect or an unprotect
261 $reason: Reason for protect
262 $moveonly: boolean whether this is for move only or not
264 'ArticleProtectComplete': after an article is protected
265 $article: the article that was protected
266 $user: the user who did the protection
267 $protect: boolean whether it was a protect or an unprotect
268 $reason: Reason for protect
269 $moveonly: boolean whether it was for move only or not
271 'ArticleSave': before an article is saved
272 $article: the article (object) being saved
273 $user: the user (object) saving the article
274 $text: the new article text
275 $summary: the article summary (comment)
280 'ArticleSaveComplete': after an article is saved
281 $article: the article (object) saved
282 $user: the user (object) who saved the article
283 $text: the new article text
284 $summary: the article summary (comment)
289 'ArticleUndeleted': When one or more revisions of an article are restored
290 $title: Title corresponding to the article restored
291 $create: Whether or not the restoration caused the page to be created
292 (i.e. it didn't exist before)
294 'AuthPluginSetup': update or replace authentication plugin object ($wgAuth)
295 Gives a chance for an extension to set it programattically to a variable class.
296 &$auth: the $wgAuth object, probably a stub
298 'AutoAuthenticate': called to authenticate users on external/environmental means
299 $user: writes user object to this parameter
301 'BadImage': When checking against the bad image list
302 $name: Image name being checked
303 &$bad: Whether or not the image is "bad"
305 Change $bad and return false to override. If an image is "bad", it is not
306 rendered inline in wiki pages or galleries in category pages.
308 'BlockIp': before an IP address or user is blocked
309 $block: the Block object about to be saved
310 $user: the user _doing_ the block (not the one being blocked)
312 'BlockIpComplete': after an IP address or user is blocked
313 $block: the Block object that was saved
314 $user: the user who did the block (not the one being blocked)
316 'BookInformation': Before information output on Special:Booksources
317 $isbn: ISBN to show information for
318 $output: OutputPage object in use
320 'DiffViewHeader': called before diff display
321 $diff: DifferenceEngine object that's calling
322 $oldRev: Revision object of the "old" revision (may be null/invalid)
323 $newRev: Revision object of the "new" revision
325 'EditPage::attemptSave': called before an article is
326 saved, that is before insertNewArticle() is called
327 &$editpage_Obj: the current EditPage object
329 'EditFormPreloadText': Allows population of the edit form when creating new pages
330 &$text: Text to preload with
331 &$title: Title object representing the page being created
333 'EditFilter': Perform checks on an edit
334 $editor: Edit form (see includes/EditPage.php)
335 $text: Contents of the edit box
336 $section: Section being edited
337 &$error: Error message to return
339 Return false to halt editing; you'll need to handle error messages, etc. yourself.
340 Alternatively, modifying $error and returning true will cause the contents of $error
341 to be echoed at the top of the edit form as wikitext. Return true without altering
342 $error to allow the edit to proceed.
344 'EmailConfirmed': When checking that the user's email address is "confirmed"
345 $user: User being checked
346 $confirmed: Whether or not the email address is confirmed
347 This runs before the other checks, such as anonymity and the real check; return
348 true to allow those checks to occur, and false if checking is done.
350 'EmailUser': before sending email from one user to another
351 $to: address of receiving user
352 $from: address of sending user
353 $subject: subject of the mail
354 $text: text of the mail
356 'EmailUserComplete': after sending email from one user to another
357 $to: address of receiving user
358 $from: address of sending user
359 $subject: subject of the mail
360 $text: text of the mail
362 'FetchChangesList': When fetching the ChangesList derivative for a particular user
363 &$user: User the list is being fetched for
364 &$skin: Skin object to be used with the list
365 &$list: List object (defaults to NULL, change it to an object instance and return
366 false override the list derivative used)
368 'GetInternalURL': modify fully-qualified URLs used for squid cache purging
369 $title: Title object of page
370 $url: string value as output (out parameter, can modify)
371 $query: query options passed to Title::getInternalURL()
373 'GetLocalURL': modify local URLs as output into page links
374 $title: Title object of page
375 $url: string value as output (out parameter, can modify)
376 $query: query options passed to Title::getLocalURL()
378 'GetFullURL': modify fully-qualified URLs used in redirects/export/offsite data
379 $title: Title object of page
380 $url: string value as output (out parameter, can modify)
381 $query: query options passed to Title::getFullURL()
383 'LogPageValidTypes': action being logged. DEPRECATED: Use $wgLogTypes
384 &$type: array of strings
386 'LogPageLogName': name of the logging page(s). DEPRECATED: Use $wgLogNames
387 &$typeText: array of strings
389 'LogPageLogHeader': strings used by wfMsg as a header. DEPRECATED: Use $wgLogHeaders
390 &$headerText: array of strings
392 'LogPageActionText': strings used by wfMsg as a header. DEPRECATED: Use $wgLogActions
393 &$actionText: array of strings
395 'MarkPatrolled': before an edit is marked patrolled
396 $rcid: ID of the revision to be marked patrolled
397 $user: the user (object) marking the revision as patrolled
398 $wcOnlySysopsCanPatrol: config setting indicating whether the user
399 needs to be a sysop in order to mark an edit patrolled
401 'MarkPatrolledComplete': after an edit is marked patrolled
402 $rcid: ID of the revision marked as patrolled
403 $user: user (object) who marked the edit patrolled
404 $wcOnlySysopsCanPatrol: config setting indicating whether the user
405 must be a sysop to patrol the edit
407 'MathAfterTexvc': after texvc is executed when rendering mathematics
408 $mathRenderer: instance of MathRenderer
409 $errmsg: error message, in HTML (string). Nonempty indicates failure
410 of rendering the formula
412 'OutputPageBeforeHTML': a page has been processed by the parser and
413 the resulting HTML is about to be displayed.
414 $parserOutput: the parserOutput (object) that corresponds to the page
415 $text: the text that will be displayed, in HTML (string)
417 'PageRenderingHash': alter the parser cache option hash key
418 A parser extension which depends on user options should install
419 this hook and append its values to the key.
420 $hash: reference to a hash key string which can be modified
422 'PersonalUrls': Alter the user-specific navigation links (e.g. "my page,
423 my talk page, my contributions" etc).
425 &$personal_urls: Array of link specifiers (see SkinTemplate.php)
426 &$title: Title object representing the current page
428 'PingLimiter': Allows extensions to override the results of User::pingLimiter()
429 &$user : User performing the action
430 $action : Action being performed
431 &$result : Whether or not the action should be prevented
432 Change $result and return false to give a definitive answer, otherwise
433 the built-in rate limiting checks are used, if enabled.
435 'PreferencesUserInformationPanel': Add HTML bits to user information list in preferences form
436 $form : PreferencesForm object
437 &$html : HTML to append to
439 'RawPageViewBeforeOutput': Right before the text is blown out in action=raw
440 &$obj: RawPage object
441 &$text: The text that's going to be the output
443 'SiteNoticeBefore': Before the sitenotice/anonnotice is composed
444 &$siteNotice: HTML returned as the sitenotice
445 Return true to allow the normal method of notice selection/rendering to work,
446 or change the value of $siteNotice and return false to alter it.
448 'SiteNoticeAfter': After the sitenotice/anonnotice is composed
449 &$siteNotice: HTML sitenotice
450 Alter the contents of $siteNotice to add to/alter the sitenotice/anonnotice.
452 'SkinTemplateOutputPageBeforeExec': Before SkinTemplate::outputPage() starts page output
453 &$sktemplate: SkinTemplate object
454 &$tpl: Template engine object
456 'TitleMoveComplete': after moving an article (title)
459 $user: user who did the move
460 $pageid: database ID of the page that's been moved
461 $redirid: database ID of the created redirect
463 'UnknownAction': An unknown "action" has occured (useful for defining
466 $article: article "acted on"
468 'UnwatchArticle': before a watch is removed from an article
470 $article: article object to be removed
472 'UnwatchArticle': after a watch is removed from an article
473 $user: user that was watching
474 $article: article object removed
476 'UploadForm:initial': before the upload form is generated
477 $form: UploadForm object
478 You might set the member-variables $uploadFormTextTop and
479 $uploadFormTextAfterSummary to inject text (HTML) either before
480 or after the editform.
482 'UploadForm:BeforeProcessing': at the beginning of processUpload()
483 $form: UploadForm object
484 Lets you poke at member variables like $mUploadDescription before the
487 'UploadVerification': additional chances to reject an uploaded file
488 string $saveName: destination file name
489 string $tempName: filesystem path to the temporary file for checks
490 string &$error: output: HTML error to show if upload canceled by returning false
492 'UploadComplete': Upon completion of a file upload
493 $image: Image object representing the file that was uploaded
495 'UserCan': To interrupt/advise the "user can do X to Y article" check
496 $title: Title object being checked against
497 $user : Current user object
498 $action: Action being checked
499 $result: Pointer to result returned if hook returns false. If null is returned,
500 UserCan checks are continued by internal code
502 'UserCreateForm': change to manipulate the login form
503 $template: SimpleTemplate instance for the form
505 'UserLoginComplete': after a user has logged in
506 $user: the user object that was created on login
508 'UserLoginForm': change to manipulate the login form
509 $template: SimpleTemplate instance for the form
511 'UserLogout': before a user logs out
512 $user: the user object that is about to be logged out
514 'UserLogoutComplete': after a user has logged out
515 $user: the user object _after_ logout (won't have name, ID, etc.)
517 'UserRights': After a user's group memberships are changed
518 $user : User object that was changed
519 $add : Array of strings corresponding to groups added
520 $remove: Array of strings corresponding to groups removed
522 'WatchArticle': before a watch is added to an article
523 $user: user that will watch
524 $article: article object to be watched
526 'WatchArticleComplete': after a watch is added to an article
527 $user: user that watched
528 $article: article object watched
530 'UnwatchArticleComplete': after a watch is removed from an article
531 $user: user that watched
532 $article: article object that was watched
534 'CategoryPageView': before viewing a categorypage in CategoryPage::view
535 $catpage: CategoryPage instance
537 'SkinTemplateContentActions': after building the $content_action array right
538 before returning it, see Content_action.php in
539 the extensions/examples/ directory
540 ( http://svn.wikimedia.org/viewvc/mediawiki/trunk/extensions/examples/ )
541 for a demonstration of how to use this hook.
542 $content_actions: The array of content actions
544 'BeforePageDisplay': Called just before outputting a page (all kinds of,
545 articles, special, history, preview, diff, edit, ...)
546 Can be used to set custom CSS/JS
547 $out: OutputPage object
549 More hooks might be available but undocumented, you can execute
550 ./maintenance/findhooks.php to find hidden one.