Manual:Hooks/EditPage::showEditForm:fields

Details
This hook is called before edit box and the toolbar are published.

return value is ignored (should always return true)
 * $editpage - The EditPage object.
 * $output - the OutputPage object (added in version 1.12.0)

Example
If you wanted to have your edit page indexed by search engines (e.g. so that the Internet Archive would store the raw wikitext of your pages), you might add this to LocalSettings.php: