public static function clientIP() : string
    {
        if (!empty($_SERVER['HTTP_CF_CONNECTING_IP'])) {
            return $_SERVER['HTTP_CF_CONNECTING_IP'];
        } elseif (!empty($_SERVER['HTTP_CLIENT_IP'])) {
            return $_SERVER['HTTP_CLIENT_IP'];
        } elseif (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
            return $_SERVER['HTTP_X_FORWARDED_FOR'];
        }

        return $_SERVER['REMOTE_ADDR'];
    }