echo 'User IP - '.$_SERVER['REMOTE_ADDR']; // 服务器在局域网的话，那么显示的则是内网IP 。
// 如果服务器在外网的话，那么访问的话获得的是外网的IP，无法获取内网IP。

function getUserIpAddr(){

    if(!empty($_SERVER['HTTP_CLIENT_IP'])){

        //ip from share internet

        $ip = $_SERVER['HTTP_CLIENT_IP'];

    }elseif(!empty($_SERVER['HTTP_X_FORWARDED_FOR'])){

        //ip pass from proxy

        $ip = $_SERVER['HTTP_X_FORWARDED_FOR'];

    }else{

        $ip = $_SERVER['REMOTE_ADDR'];

    }

    return $ip;

}

echo 'User Real IP - '.getUserIpAddr();