获取客户端ip

/**获取客户端ip
     * @return string
     */
    protected function getClientIp()
    {
        if (getenv('HTTP_CLIENT_IP')) {
            $ip = getenv('HTTP_CLIENT_IP');
        } else if (getenv('HTTP_X_FORWARDED_FOR')) {
            $ip = getenv('HTTP_X_FORWARDED_FOR');
        } else if (getenv('REMOTE_ADDR')) {
            $ip = getenv('REMOTE_ADDR');
        } else {
            $ip = $_SERVER['REMOTE_ADDR'];
        }
        return $ip;
    }