static function add_ajax_action_static(
            $tag,
            $function_to_add,
            $priority = WP_FS__DEFAULT_PRIORITY,
            $module_id = null
        ) {
            self::$_static_logger->entrance( $tag );

            if ( ! self::is_ajax_action_static( $tag, $module_id ) ) {
                return false;
            }

            add_action(
                'wp_ajax_' . self::get_ajax_action_static( $tag, $module_id ),
                $function_to_add,
                $priority,
                0
            );

            self::$_static_logger->info( "$tag AJAX callback action added." );

            return true;
        }