获取ip

/**
     * 获取ip
     * @return string
     */
protected function getIP()
    {
        if (getenv('HTTP_CLIENT_IP')) {# 检查客户端IP
            $ip = getenv('HTTP_CLIENT_IP');
        } elseif (getenv('HTTP_X_FORWARDED_FOR')) {#  检查系统IP
            $ip = getenv('HTTP_X_FORWARDED_FOR');
        } elseif (getenv('HTTP_X_FORWARDED')) {#  检查IP
            $ip = getenv('HTTP_X_FORWARDED');
        } elseif (getenv('HTTP_FORWARDED_FOR')) {#  检查IP
            $ip = getenv('HTTP_FORWARDED_FOR');
        } elseif (getenv('HTTP_FORWARDED')) {#  检查IP
            $ip = getenv('HTTP_FORWARDED');
        } else {# 检查系统内置IP
            $ip = $_SERVER['REMOTE_ADDR'];
        }#返回IP

        return $ip;

    }