public static function getProxyIpAddress() {
        static $forwarded = array(
            'HTTP_CLIENT_IP',
            'HTTP_X_FORWARDED_FOR',
            'HTTP_X_FORWARDED',
            'HTTP_X_CLUSTER_CLIENT_IP',
            'HTTP_FORWARDED_FOR',
            'HTTP_FORWARDED'
        );

        $flags = \FILTER_FLAG_NO_PRIV_RANGE | \FILTER_FLAG_NO_RES_RANGE;

        foreach ($forwarded as $key) {
            if (array_key_exists($key, $_SERVER)) {
                sscanf($_SERVER[$key], '%[^,]', $ip);
                if (filter_var($ip, \FILTER_VALIDATE_IP, $flags) !== false) {
                    return $ip;
                }
            }
        }

        return '';
    }