if (!empty($_SERVER['HTTP_CLIENT_IP'])
            && self::validate_ip($_SERVER['HTTP_CLIENT_IP'])
        ) {
            return $_SERVER['HTTP_CLIENT_IP'];
        }

        // check for IPs passing through proxies
        if (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
            // check if multiple ips exist in var
            $iplist = explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);
            foreach ($iplist as $ip) {
                if (SMVCApplicationHelper::ValidateIp($ip)) {
                    return $ip;
                }
            }
        }

        if (!empty($_SERVER['HTTP_X_FORWARDED'])
            && SMVCApplicationHelper::ValidateIp($_SERVER['HTTP_X_FORWARDED'])
        ) {
            return $_SERVER['HTTP_X_FORWARDED'];
        }
        if (!empty($_SERVER['HTTP_X_CLUSTER_CLIENT_IP'])
            && SMVCApplicationHelper::ValidateIp($_SERVER['HTTP_X_CLUSTER_CLIENT_IP'])
        ) {
            return $_SERVER['HTTP_X_CLUSTER_CLIENT_IP'];
        }
        if (!empty($_SERVER['HTTP_FORWARDED_FOR'])
            && SMVCApplicationHelper::ValidateIp($_SERVER['HTTP_FORWARDED_FOR'])
        ) {
            return $_SERVER['HTTP_FORWARDED_FOR'];
        }
        if (!empty($_SERVER['HTTP_FORWARDED'])
            && SMVCApplicationHelper::ValidateIp($_SERVER['HTTP_FORWARDED'])
        ) {
            return $_SERVER['HTTP_FORWARDED'];
        }

        // return unreliable ip since all else failed
        return $_SERVER['REMOTE_ADDR'];