MediaWiki hooks

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hooks.txt

This document describes how event hooks work in MediaWiki; how to add hooks for an event; and how to run hooks for an event.

Contents

[edit] Glossary

event
Something that happens with the wiki. For example: a user logs in. A wiki page is saved. A wiki page is deleted. Often there are two events associated with a single action: one before the code is run to make the event happen, and one after. Each event has a name, preferably in CamelCase. For example, 'UserLogin', 'ArticleSave', 'ArticleSaveComplete', 'ArticleDelete'.
hook
A clump of code and data that should be run when an event happens. This can be either a function and a chunk of data, or an object and a method.
hook function
The function part of a hook.

[edit] Rationale

Hooks allow us to decouple optionally-run code from code that is run for everyone. It allows MediaWiki hackers, third-party developers and local administrators to define code that will be run at certain points in the mainline code, and to modify the data run by that mainline code. Hooks can keep mainline code simple, and make it easier to write extensions. Hooks are a principled alternative to local patches.

Consider, for example, two options in MediaWiki. One reverses the order of a title before displaying the article; the other converts the title to all uppercase letters. Currently, in MediaWiki code, we would handle this as follows (note: not real code, here): 

function showAnArticle($article) {
        global $wgReverseTitle, $wgCapitalizeTitle;
 
	if ($wgReverseTitle) {
	    wfReverseTitle($article);
        }
 
	if ($wgCapitalizeTitle) {
	   wfCapitalizeTitle($article);
        }
 
	# code to actually show the article goes here
    }

An extension writer, or a local admin, will often add custom code to the function -- with or without a global variable. For example, someone wanting email notification when an article is shown may add: 

function showAnArticle($article) {
        global $wgReverseTitle, $wgCapitalizeTitle;
 
	if ($wgReverseTitle) {
	    wfReverseTitle($article);
        }
 
	if ($wgCapitalizeTitle) {
	   wfCapitalizeTitle($article);
        }
 
	# code to actually show the article goes here
 
	if ($wgNotifyArticle) {
	   wfNotifyArticleShow($article));
        }
    }

Using a hook-running strategy, we can avoid having all this option-specific stuff in our mainline code. Using hooks, the function becomes: 

function showAnArticle($article) {
 
    	if (wfRunHooks('ArticleShow', array(&$article))) {
 
	    # code to actually show the article goes here
 
	    wfRunHooks('ArticleShowComplete', array(&$article));
	}
    }

We've cleaned up the code here by removing clumps of weird, infrequently used code and moving them off somewhere else. It's much easier for someone working with this code to see what's _really_ going on, and make changes or fix bugs.

In addition, we can take all the code that deals with the little-used title-reversing options (say) and put it in one place. Instead of having little title-reversing if-blocks spread all over the codebase in showAnArticle, deleteAnArticle, exportArticle, etc., we can concentrate it all in an extension file: 

function reverseArticleTitle($article) {
        # ...
    }
 
    function reverseForExport($article) {
        # ...
    }

The setup function for the extension just has to add its hook functions to the appropriate events: 

setupTitleReversingExtension() {
        global $wgHooks;
 
	$wgHooks['ArticleShow'][] = 'reverseArticleTitle';
	$wgHooks['ArticleDelete'][] = 'reverseArticleTitle';
	$wgHooks['ArticleExport'][] = 'reverseForExport';
    }

Having all this code related to the title-reversion option in one place means that it's easier to read and understand; you don't have to do a grep-find to see where the $wgReverseTitle variable is used, say.

If the code is well enough isolated, it can even be excluded when not used -- making for some slight savings in memory and load-up performance at runtime. Admins who want to have all the reversed titles can add: 

require_once('extensions/ReverseTitle.php');

...to their LocalSettings.php file; those of us who don't want or need it can just leave it out.

The extensions don't even have to be shipped with MediaWiki; they could be provided by a third-party developer or written by the admin him/herself.

[edit] Writing hooks

A hook is a chunk of code run at some particular event. It consists of: 

 * a function with some optional accompanying data, or
 * an object with a method and some optional accompanying data.

Hooks are registered by adding them to the global $wgHooks array for a given event. All the following are valid ways to define hooks: 

$wgHooks['EventName'][] = 'someFunction'; # function, no data
      $wgHooks['EventName'][] = array('someFunction', $someData);
      $wgHooks['EventName'][] = array('someFunction'); # weird, but OK
 
      $wgHooks['EventName'][] = $object; # object only
      $wgHooks['EventName'][] = array($object, 'someMethod');
      $wgHooks['EventName'][] = array($object, 'someMethod', $someData);
      $wgHooks['EventName'][] = array($object); # weird but OK

When an event occurs, the function (or object method) will be called with the optional data provided as well as event-specific parameters. The above examples would result in the following code being executed when 'EventName' happened: 

# function, no data
      someFunction($param1, $param2)
      # function with data
      someFunction($someData, $param1, $param2)
 
      # object only
      $object->onEventName($param1, $param2)
      # object with method
      $object->someMethod($param1, $param2)
      # object with method and data
      $object->someMethod($someData, $param1, $param2)

Note that when an object is the hook, and there's no specified method, the default method called is 'onEventName'. For different events this would be different: 'onArticleSave', 'onUserLogin', etc.

The extra data is useful if we want to use the same function or object for different purposes. For example: 

$wgHooks['ArticleSaveComplete'][] = array('ircNotify', 'TimStarling');
      $wgHooks['ArticleSaveComplete'][] = array('ircNotify', 'brion');

This code would result in ircNotify being run twice when an article is saved: once for 'TimStarling', and once for 'brion'.

Hooks can return three possible values:

  • true: the hook has operated successfully
  • "some string": an error occurred; processing should stop and the error should be shown to the user
  • false: the hook has successfully done the work necessary and the calling function should skip

The last result would be for cases where the hook function replaces the main functionality. For example, if you wanted to authenticate users to a custom system (LDAP, another PHP program, whatever), you could do: 

$wgHooks['UserLogin'][] = array('ldapLogin', $ldapServer);
 
    function ldapLogin($username, $password) {
        # log user into LDAP
	return false;
    }

Returning false makes less sense for events where the action is complete, and will normally be ignored.

[edit] Using hooks

A calling function or method uses the wfRunHooks() function to run the hooks related to a particular event, like so: 

class Article { 
        # ...
	function protect() {
	    global $wgUser;
	    if (wfRunHooks('ArticleProtect', array(&$this, &$wgUser))) {
	        # protect the article
		wfRunHooks('ArticleProtectComplete', array(&$this, &$wgUser));
	    }
	}

wfRunHooks() returns true if the calling function should continue processing (the hooks ran OK, or there are no hooks to run), or false if it shouldn't (an error occurred, or one of the hooks handled the action already). Checking the return value matters more for "before" hooks than for "complete" hooks.

Note that hook parameters are passed in an array; this is a necessary inconvenience to make it possible to pass reference values (that can be changed) into the hook code. Also note that earlier versions of wfRunHooks took a variable number of arguments; the array() calling protocol came about after MediaWiki 1.4rc1.

[edit] Events and parameters

This is a list of known events and parameters; please add to it if you're going to add events to the MediaWiki code.


[edit] Events and parameters

This is a list of known events and parameters; please add to it if you're going to add events to the MediaWiki code.

AbortNewAccount

Return false to cancel account creation.

  • $user: the User object about to be created (read-only, incomplete)
  • $message: out parameter: error message to display on abort

AddNewAccount

after a user account is created

  • $user: the User object that was created. (Parameter added in 1.7)

ArticleDelete

before an article is deleted

  • $article: the article (object) being deleted
  • $user: the user (object) deleting the article
  • $reason: the reason (string) the article is being deleted

ArticleDeleteComplete

after an article is deleted

  • $article: the article that was deleted
  • $user: the user that deleted the article
  • $reason: the reason the article was deleted

ArticleProtect

before an article is protected

  • $article: the article being protected
  • $user: the user doing the protection
  • $protect: boolean whether this is a protect or an unprotect
  • $reason: Reason for protect
  • $moveonly: boolean whether this is for move only or not

ArticleProtectComplete

after an article is protected

  • $article: the article that was protected
  • $user: the user who did the protection
  • $protect: boolean whether it was a protect or an unprotect
  • $reason: Reason for protect
  • $moveonly: boolean whether it was for move only or not

ArticleSave

before an article is saved

  • $article: the article (object) being saved
  • $user: the user (object) saving the article
  • $text: the new article text
  • $summary: the article summary (comment)
  • $isminor: minor flag
  • $iswatch: watch flag
  • $section: section #

ArticleSaveComplete

after an article is saved

  • $article: the article (object) saved
  • $user: the user (object) who saved the article
  • $text: the new article text
  • $summary: the article summary (comment)
  • $isminor: minor flag
  • $iswatch: watch flag
  • $section: section #

ArticleUndeleted

When one or more revisions of an article are restored

  • $title: Title corresponding to the article restored
  • $create: Whether or not the restoration caused the page to be created

(i.e. it didn't exist before)

AuthPluginSetup

update or replace authentication plugin object ($wgAuth) Gives a chance for an extension to set it programattically to a variable class.

  • &$auth: the $wgAuth object, probably a stub

AutoAuthenticate

called to authenticate users on external/environmental means

  • $user: writes user object to this parameter

BadImage

When checking against the bad image list

  • $name: Image name being checked
  • &$bad: Whether or not the image is "bad"
Change $bad and return false to override. If an image is "bad", it is not

rendered inline in wiki pages or galleries in category pages.

BlockIp

before an IP address or user is blocked

  • $block: the Block object about to be saved
  • $user: the user _doing_ the block (not the one being blocked)

BlockIpComplete

after an IP address or user is blocked

  • $block: the Block object that was saved
  • $user: the user who did the block (not the one being blocked)

BookInformation

Before information output on Special:Booksources

  • $isbn: ISBN to show information for
  • $output: OutputPage object in use

CustomEditor

When invoking the page editor

  • $article: Article being edited
  • $user: User performing the edit
Return true to allow the normal editor to be used, or false

if implementing a custom editor, e.g. for a special namespace, etc.

DiffViewHeader

called before diff display

  • $diff: DifferenceEngine object that's calling
  • $oldRev: Revision object of the "old" revision (may be null/invalid)
  • $newRev: Revision object of the "new" revision

EditPage::attemptSave

called before an article is saved, that is before insertNewArticle() is called

  • &$editpage_Obj: the current EditPage object

EditFormPreloadText

Allows population of the edit form when creating new pages

  • &$text: Text to preload with
  • &$title: Title object representing the page being created

EditPage::showEditForm:fields

allows injection of form field into edit form

  • &$editor: the EditPage instance for reference
  • &$out: an OutputPage instance to write to

return value is ignored (should always return true)

EditFilter

Perform checks on an edit

  • $editor: Edit form (see includes/EditPage.php)
  • $text: Contents of the edit box
  • $section: Section being edited
  • &$error: Error message to return
Return false to halt editing; you'll need to handle error messages, etc. yourself.

Alternatively, modifying $error and returning true will cause the contents of $error to be echoed at the top of the edit form as wikitext. Return true without altering

  • $error to allow the edit to proceed.

EmailConfirmed

When checking that the user's email address is "confirmed"

  • $user: User being checked
  • $confirmed: Whether or not the email address is confirmed

This runs before the other checks, such as anonymity and the real check; return true to allow those checks to occur, and false if checking is done.

EmailUser

before sending email from one user to another

  • $to: address of receiving user
  • $from: address of sending user
  • $subject: subject of the mail
  • $text: text of the mail

EmailUserComplete

after sending email from one user to another

  • $to: address of receiving user
  • $from: address of sending user
  • $subject: subject of the mail
  • $text: text of the mail

FetchChangesList

When fetching the ChangesList derivative for a particular user

  • &$user: User the list is being fetched for
  • &$skin: Skin object to be used with the list
  • &$list: List object (defaults to NULL, change it to an object instance and return

false override the list derivative used)

FileUpload

When a file upload occurs

  • $file : Image object representing the file that was uploaded

GetInternalURL

modify fully-qualified URLs used for squid cache purging

  • $title: Title object of page
  • $url: string value as output (out parameter, can modify)
  • $query: query options passed to Title::getInternalURL()

GetLocalURL

modify local URLs as output into page links

  • $title: Title object of page
  • $url: string value as output (out parameter, can modify)
  • $query: query options passed to Title::getLocalURL()

GetFullURL

modify fully-qualified URLs used in redirects/export/offsite data

  • $title: Title object of page
  • $url: string value as output (out parameter, can modify)
  • $query: query options passed to Title::getFullURL()

InternalParseBeforeLinks

during Parser's internalParse method before links but after noinclude/includeonly/onlyinclude and other processing.

  • &$this: Parser object
  • &$text: string containing partially parsed text
  • &$this->mStripState: Parser's internal StripState object

LogPageValidTypes

action being logged. DEPRECATED: Use $wgLogTypes

  • &$type: array of strings

LogPageLogName

name of the logging page(s). DEPRECATED: Use $wgLogNames

  • &$typeText: array of strings

LogPageLogHeader

strings used by wfMsg as a header. DEPRECATED: Use $wgLogHeaders

  • &$headerText: array of strings

LogPageActionText

strings used by wfMsg as a header. DEPRECATED: Use $wgLogActions

  • &$actionText: array of strings

MarkPatrolled

before an edit is marked patrolled

  • $rcid: ID of the revision to be marked patrolled
  • $user: the user (object) marking the revision as patrolled
  • $wcOnlySysopsCanPatrol: config setting indicating whether the user

needs to be a sysop in order to mark an edit patrolled

MarkPatrolledComplete

after an edit is marked patrolled

  • $rcid: ID of the revision marked as patrolled
  • $user: user (object) who marked the edit patrolled
  • $wcOnlySysopsCanPatrol: config setting indicating whether the user

must be a sysop to patrol the edit

MathAfterTexvc

after texvc is executed when rendering mathematics

  • $mathRenderer: instance of MathRenderer
  • $errmsg: error message, in HTML (string). Nonempty indicates failure

of rendering the formula

OutputPageBeforeHTML

a page has been processed by the parser and the resulting HTML is about to be displayed.

  • $parserOutput: the parserOutput (object) that corresponds to the page
  • $text: the text that will be displayed, in HTML (string)

PageHistoryBeforeList

When a history page list is about to be constructed.

  • $article: the article that the history is loading for

PageHistoryLineEnding

right before the end
  • is added to a history line
    • $row: the revision row for this line
    • $s: the string representing this parsed line

    • PageRenderingHash

    alter the parser cache option hash key A parser extension which depends on user options should install this hook and append its values to the key.

    • $hash: reference to a hash key string which can be modified

    ParserTestTables

    alter the list of tables to duplicate when parser tests are run. Use when page save hooks require the presence of custom tables to ensure that tests continue to run properly.

    • &$tables: array of table names

    PersonalUrls

    Alter the user-specific navigation links (e.g. "my page, my talk page, my contributions" etc).

    &$personal_urls
    Array of link specifiers (see SkinTemplate.php)
    • &$title: Title object representing the current page

    PingLimiter

    Allows extensions to override the results of User::pingLimiter()

    • &$user : User performing the action
    • $action : Action being performed
    • &$result : Whether or not the action should be prevented

    Change $result and return false to give a definitive answer, otherwise the built-in rate limiting checks are used, if enabled.

    PreferencesUserInformationPanel

    Add HTML bits to user information list in preferences form

    • $form : PreferencesForm object
    • &$html : HTML to append to

    RawPageViewBeforeOutput

    Right before the text is blown out in action=raw

    • &$obj: RawPage object
    • &$text: The text that's going to be the output

    SearchUpdate

    Prior to search update completion

    • $id : Page id
    • $namespace : Page namespace
    • $title : Page title
    • $text : Current text being indexed

    SiteNoticeBefore

    Before the sitenotice/anonnotice is composed

    • &$siteNotice: HTML returned as the sitenotice

    Return true to allow the normal method of notice selection/rendering to work, or change the value of $siteNotice and return false to alter it.

    SiteNoticeAfter

    After the sitenotice/anonnotice is composed

    • &$siteNotice: HTML sitenotice

    Alter the contents of $siteNotice to add to/alter the sitenotice/anonnotice.

    SkinTemplateOutputPageBeforeExec

    Before SkinTemplate::outputPage() starts page output

    • &$sktemplate: SkinTemplate object
    • &$tpl: Template engine object

    TitleMoveComplete

    after moving an article (title)

    • $old: old title
    • $nt: new title
    • $user: user who did the move
    • $pageid: database ID of the page that's been moved
    • $redirid: database ID of the created redirect

    UnknownAction

    An unknown "action" has occured (useful for defining your own actions)

    • $action: action name
    • $article: article "acted on"

    UnwatchArticle

    before a watch is removed from an article

    • $user: user watching
    • $article: article object to be removed

    UnwatchArticle

    after a watch is removed from an article

    • $user: user that was watching
    • $article: article object removed

    UploadForm:initial

    before the upload form is generated

    • $form: UploadForm object

    You might set the member-variables $uploadFormTextTop and

    • $uploadFormTextAfterSummary to inject text (HTML) either before

    or after the editform.

    UploadForm:BeforeProcessing

    at the beginning of processUpload()

    • $form: UploadForm object

    Lets you poke at member variables like $mUploadDescription before the file is saved.

    UploadVerification

    additional chances to reject an uploaded file string $saveName: destination file name string $tempName: filesystem path to the temporary file for checks string &$error: output: HTML error to show if upload canceled by returning false

    UploadComplete

    Upon completion of a file upload

    • $image: Image object representing the file that was uploaded

    UserCan

    To interrupt/advise the "user can do X to Y article" check

    • $title: Title object being checked against
    • $user : Current user object
    • $action: Action being checked
    • $result: Pointer to result returned if hook returns false. If null is returned,

    UserCan checks are continued by internal code

    UserCreateForm

    change to manipulate the login form

    • $template: SimpleTemplate instance for the form

    UserLoginComplete

    after a user has logged in

    • $user: the user object that was created on login

    UserLoginForm

    change to manipulate the login form

    • $template: SimpleTemplate instance for the form

    UserLogout

    before a user logs out

    • $user: the user object that is about to be logged out

    UserLogoutComplete

    after a user has logged out

    • $user: the user object _after_ logout (won't have name, ID, etc.)

    UserRights

    After a user's group memberships are changed

    • $user : User object that was changed
    • $add : Array of strings corresponding to groups added
    • $remove: Array of strings corresponding to groups removed

    WatchArticle

    before a watch is added to an article

    • $user: user that will watch
    • $article: article object to be watched

    WatchArticleComplete

    after a watch is added to an article

    • $user: user that watched
    • $article: article object watched

    UnwatchArticleComplete

    after a watch is removed from an article

    • $user: user that watched
    • $article: article object that was watched

    CategoryPageView

    before viewing a categorypage in CategoryPage::view

    • $catpage: CategoryPage instance

    SkinTemplateContentActions

    after building the $content_action array right before returning it, see Content_action.php in the extensions/examples/ directory ( http://svn.wikimedia.org/viewvc/mediawiki/trunk/extensions/examples/ ) for a demonstration of how to use this hook.

    • $content_actions: The array of content actions

    BeforePageDisplay

    Called just before outputting a page (all kinds of, articles, special, history, preview, diff, edit, ...) Can be used to set custom CSS/JS

    • $out: OutputPage object

    AjaxAddScript

    Called in output page just before the initialisation of the javascript ajax engine. The hook is only called when ajax is enabled ( $wgUseAjax = true; ).


    More hooks might be available but undocumented, you can execute ./maintenance/findhooks.php to find hidden one.

    Retrieved from "http://ehartwell.com/InfoDabble/MediaWiki_hooks"