Wikimedia Bugzilla is closed!

The deprecated is_a() function is used in StubObjects.php line 27 in the
isRealObject function.
The is_a() function is deprecated as of PHP 5 in favor of the instanceof type
operator.
(http://php.net/manual/en/function.is-a.php)

The correct function should look like:
	static function isRealObject( $obj ) {
		return is_object( $obj ) && !($obj instanceof StubObject) ;
	}

(I tested with this code above, and it is working fine.)