Hooks can return three possible values:
- * true: the hook has operated successfully
+ * No return value (or null): the hook has operated successfully. Previously,
+ true was required. This is the default since MediaWiki 1.23.
* "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
'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.
+Unlike for example 'EditFilterMergedContent' this also being run on undo.
$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