NGINX and Yii2 advance add another project in sub-directory

By usng NGINX and php-fpm, I want to add another Yii2 advance project under sub-directory like this

www.xyz.net - frontend project A, root at /var/www/html  
www.xyz.net/admin - backend project A, root at /var/www/html   
www.xyz.net/old - frontend project B, root at /var/www/old  
www.xyz.net/old/admin - backend project B, root at /var/www/old 

The below is the nginx configuration which I am using for 1 project How can I modify it for adding another Yii2 advance project in sub-directory?

server {
  server_name www.xyz.net;
  listen 80;
  set $base_root /var/www/html;
  root $base_root;
  charset utf-8;
  index index.php index.html index.htm;
  client_max_body_size 128M;

  location / {
    root $base_root/frontend/web;
    try_files $uri $uri/ /frontend/web/index.php$is_args$args;
    location ~ ^/assets/.+\.php(/|$) {
      deny all;
    }
  }

  location /admin {
    alias $base_root/backend/web/;
    location = /admin/ {
      return 301 /admin;
    }

    location = /admin {
      try_files $uri /backend/web/index.php$is_args$args;
    }  

    try_files $uri $uri/ /backend/web/index.php$is_args$args;
    location ~ ^/admin/assets/.+\.php(/|$) {
      deny all;
    }
  }

  location ~ ^/.+\.php(/|$) {
    rewrite (?!^/((frontend|backend)/web|admin))^ /frontend/web$uri break;
    rewrite (?!^/backend/web)^/admin(/.+)$ /backend/web$1 break;
    fastcgi_pass php:9000;
    fastcgi_split_path_info ^(.+\.php)(.*)$;
    include /etc/nginx/fastcgi_params;
    fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
    try_files $fastcgi_script_name =404;
  }

  location ~ /\. {
    deny all;
  }
}