public static function registerEngine($engineClass, $priority)
    {
        if (!is_int($priority)) {
            trigger_error('Priority must be integer', E_USER_WARNING);

            return;
        }
        if (array_key_exists($priority, self::$registeredEngines)) {
            trigger_error('Priority already taken', E_USER_WARNING);

            return;
        }
        if (!class_exists($engineClass)) {
            trigger_error('Engine does not exist', E_USER_WARNING);

            return;
        }
        self::$registeredEngines[$priority] = $engineClass;
    }