yii バックエンドで独立したサブドメイン名を設定する方法

#START-SITEserver {
    listen 80;
    server_name  yii.com;
    access_log  logs/yii.com.access.log;
    root   D:/wwwroot/yii;
    index  index.php default.php index.html index.htm default.html default.htm;    
    include rewrite/yii.com.conf;
        
    location ~ \.php$ {
        root   D:/wwwroot/yii;
        fastcgi_pass   127.0.0.1:4570;
        fastcgi_index  index.php;
        fastcgi_param  SCRIPT_FILENAME  $document_root$fastcgi_script_name;        include        fastcgi_params;
    }

}#END-SITE

#START-SITEserver {
    charset utf-8;
    client_max_body_size 128M;

    listen 80; ## listen for ipv4
    #listen [::]:80 default_server ipv6only=on; ## listen for ipv6
    server_name back.yii.com;                     ##前台域名
    root        D:/wwwroot/yii/backend/web;   ##这是前台index地址
    index       index.php;    #access_log   D:/wwwroot/yii/access.backend.log main;
    #error_log    D:/wwwroot/yii//error.backend.log;
    location / {        # Redirect everything that isn't a real file to index.php
        try_files $uri $uri/ /index.php?$args;
    }        

    location ~ \.php$ {
        root   D:/wwwroot/yii/backend/web;
        fastcgi_pass   127.0.0.1:4570;
        fastcgi_index  index.php;
        fastcgi_param  SCRIPT_FILENAME  $document_root$fastcgi_script_name;        include        fastcgi_params;
    }    #error_page 404 /404.html;
    location ~ /\.(ht|svn|git) {
        deny all;
    }
}#END-SITE