php source files in subfolder, using nginx

tree.txt

✔ [/home/ubuntu/nginx_html/] 
$ tree
.
├── homepage.php
├── home.php
├── index.html
└── xxoo
    ├── back.php
    └── backup.php

1 directory, 5 files

✔ [/home/ubuntu/nginx_html/] 
$ wget -O - http://h2.lan/index.html
$ wget -O - http://h2.lan/home.php
$ wget -O - http://h2.lan/xxoo/back.php
$ wget -O - http://h2.lan/bak/back.php

vhost.conf

server {
	listen 80;

	server_name h2.lan;
	
	root /home/ubuntu/nginx_html/;
	
	location / {
		index index.html;
	}
	
	location ~ (home|homepage)\.php$ {
		try_files $uri =404;
		fastcgi_split_path_info ^(.+\.php)(/.+)$;
		fastcgi_pass unix:/run/php/php7.0-fpm.sock;
		fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
		include /etc/nginx/fastcgi_params;
	}

	# /bak was mapped to home/ubuntu/nginx_html/xxoo/
	location /bak{
		alias /home/ubuntu/nginx_html/xxoo/;
		
		location ~ ^/bak/(back|backup)\.php {
			try_files $uri =404;
			fastcgi_split_path_info ^(.+\.php)(/.+)$;
			fastcgi_pass unix:/run/php/php7.0-fpm.sock;
			fastcgi_param SCRIPT_FILENAME $document_root/$1.php;
			include /etc/nginx/fastcgi_params;
		}
	}
}