public static function listInstalledHandles()
    {
        if (empty(self::$_enabled_extensions) && Symphony::Database()->isConnected()) {
            self::$_enabled_extensions = Symphony::Database()->fetchCol(
                'name',
                "SELECT `name` FROM `tbl_extensions` WHERE `status` = 'enabled'"
            );
        }
        return self::$_enabled_extensions;
    }