on &action=edit.
$EditPage : the EditPage object
+'APIEditBeforeSave': before saving a page with api.php?action=edit,
+after processing request parameters. Return false to let the request
+fail, returning an error message or an <edit result="Failure"> tag
+if $resultArr was filled.
+$EditPage : the EditPage object
+$text : the new text of the article (has yet to be saved)
+$resultArr : data in this array will be added to the API result
+
'ArticleAfterFetchContent': after fetching content of an article from the database
$article: the article (object) being loaded from the database
$content: the content (string) of the article
'ArticlePurge': before executing "&action=purge"
$article: article (object) to purge
-'ArticleRevisionUndeleted' after an article revision is restored
+'ArticleRevisionVisiblitySet': called when changing visibility of one or more
+revision of an article
+&$title: title object of the article
+
+'ArticleRevisionUndeleted': after an article revision is restored
$title: the article title
$revision: the revision
$oldPageID: the page ID of the revision when archived (may be null)
$isbn: ISBN to show information for
$output: OutputPage object in use
+'BrokenLink': Before the HTML is created for a broken (i.e. red) link
+&$this: Linker instance
+$nt: the page title
+$query: the URL query string passed in
+&$u: the URL of this link
+&$style: the inline CSS style
+&$prefix: a prefix prepended to the linked text
+&$text: the text placed by the user in the wiki-link
+&$inside: any additional alphanumeric characters placed after the wiki-link,
+that are made part of the link text
+&$trail: text placed immediately after the HTML link
+
'CategoryPageView': before viewing a categorypage in CategoryPage::view
$catpage: CategoryPage instance
&$list: List object (defaults to NULL, change it to an object instance and return
false override the list derivative used)
+'FileDeleteComplete': When a file is deleted
+$file: reference to the deleted file
+$oldimage: in case of the deletion of an old image, the name of the old file
+$article: in case all revisions of the file are deleted a reference to the article
+ associated with the file.
+$user: user who performed the deletion
+$reason: reason
+
'FileUpload': When a file upload occurs
$file : Image object representing the file that was uploaded
+'FileUndeleteComplete': When a file is undeleted
+$title: title object to the file
+$fileVersions: array of undeleted versions. Empty if all versions were restored
+$user: user who performed the undeletion
+$reason: reason
+
'GetBlockedStatus': after loading blocking status of an user from the database
$user: user (object) being checked
'ParserClearState': called at the end of Parser::clearState()
$parser: Parser object being cleared
-'ParserFirstCallInit': called when the ther parser initialises for the first time
-$parser: Parser object being cleared
+'ParserFirstCallInit': called when the parser initialises for the first time
+&$parser: Parser object being cleared
'ParserGetVariableValueSwitch': called when the parser need the value of a custom magic word
$parser: Parser object
'SpecialContributionsBeforeMainOutput': Before the form on Special:Contributions
$id: User identifier
+'SpecialListusersDefaultQuery': called right before the end of UsersPager::getDefaultQuery()
+$pager: The UsersPager instance
+$query: The query array to be returned
+
+'SpecialListusersFormatRow': called right before the end of UsersPager::formatRow()
+$item: HTML to be returned. Will be wrapped in <li></li> after the hook finishes
+$row: Database row object
+
+'SpecialListusersHeader': called before closing the <fieldset> in UsersPager::getPageHeader()
+$pager: The UsersPager instance
+$out: The header HTML
+
+'SpecialListusersHeaderForm': called before adding the submit button in UsersPager::getPageHeader()
+$pager: The UsersPager instance
+$out: The header HTML
+
+'SpecialListusersQueryInfo': called right before the end of UsersPager::getQueryInfo()
+$pager: The UsersPager instance
+$query: The query array to be returned
+
'SpecialMovepageAfterMove': called after moving a page
$movePage: MovePageForm object
$oldTitle: old title (object)
'SpecialSearchNogomatch': called when user clicked the "Go" button but the target doesn't exist
$title: title object generated from the text entred by the user
+'SpecialSearchResults': called before search result display when there are matches
+$term: string of search term
+$titleMatches: empty or SearchResultSet object
+$textMatches: empty or SearchResultSet object
+
+'SpecialSearchNoResults': called before search result display when there are no matches
+$term: string of search term
+
'SpecialVersionExtensionTypes': called when generating the extensions credits, use this to change the tables headers
$extTypes: associative array of extensions types
string &$error: output: HTML error to show if upload canceled by returning false
'UploadComplete': Upon completion of a file upload
-$image: Image object representing the file that was uploaded
+$uploadForm: Upload form object. File can be accessed by $uploadForm->mLocalFile.
'userCan': To interrupt/advise the "user can do X to Y article" check.
If you want to display an error message, try getUserPermissionsErrors.