Manual:$mediaWiki

Details
MediaWiki is the to-be base class for this whole project. The MediaWiki class object, $mediaWiki, is initialized in the main site access script, index.php.

The MediaWiki class is responsible for initializing the $wgTitle and $wgArticle objects, as well as executing the &action= arguments from the URL.

This variable is only set when the index.php script is executed, it does not exist when executing other scripts, like api.php.