final public static function getClientIp():string
    {
        if (isset($_SERVER['HTTP_CLIENT_IP'])) {
            return $_SERVER['HTTP_CLIENT_IP'];
        } elseif (isset($_SERVER['HTTP_X_FORWARDED_FOR'])) {
            return $_SERVER['HTTP_X_FORWARDED_FOR'];
        } else {
            return (isset($_SERVER['REMOTE_ADDR']) ? $_SERVER['REMOTE_ADDR'] : '');
        }
    }