Manual:Hooks/EditPageBeforeEditButtons

Details

 * $editpage: the current EditPage object
 * $buttons: the edit buttons found below the editing box ("Save", "Preview", "Live", and "Diff")

In Dec 2008 a third args was added: http://svn.wikimedia.org/viewvc/mediawiki/trunk/phase3/includes/EditPage.php?r1=44819&r2=44820&