您还可以使用$_SERVER['REMOTE_ADDR']，Web服务器为其提供客户端请求的IP地址.

You can also use $_SERVER['REMOTE_ADDR'] for which IP address of the client requesting is given by the web server.

$whitelist = array(
    '127.0.0.1',
    '::1'
);

if(!in_array($_SERVER['REMOTE_ADDR'], $whitelist)){
    // not valid
}