PHP获取URL HTTP_HOST和SERVER_NAME

server{
    listen 80;
    server_name www.demo.com demo.hamm.cn;
    index index.php index.html;
    root  /home/wwwroot/demo.hamm.cn/;

    include enable-php.conf;

    location ~ .*\.(gif|jpg|jpeg|png|bmp|swf)$
    {
        expires      30d;
    }

    location ~ .*\.(js|css)?$
    {
        expires      12h;
    }

    location ~ /.well-known {
        allow all;
    }

    location ~ /\.
    {
        deny all;
    }
    location / {
        if (!-e $request_filename) {
            rewrite  ^(.*)$ /index.php?s=/$1  last;
            break;
        }
    }
    access_log off;
}

<?php 
// 访问URL http://demo.hamm.cn


echo $_SERVER['HTTP_HOST'];         //输出demo.hamm.cn
echo $_SERVER['SERVER_NAME'];       //输出www.demo.com