php - Nginx and Apache, how to configure proxy_cache?

I have Nginx installed as a front end proxy for Apache, where Apache is servicing PHP and Nginx is servicing static files. I'm having a problem configuring Nginx to cache the output from PHP into a static file. I've tried with proxy_cache, but obviously I'm doing something wrong.

Here is my base configuration:

    server {

            listen   80;

            root /var/www/web;
            index index.php index.html index.htm;

            server_name web.com;

            location / {
                    try_files $uri $uri/ /index.php;
            }


            # cache static files
            location ~*  \.(jpg|jpeg|png|gif|ico|css|js)$ {
                    expires 365d;
                    access_log off;
                    add_header Cache-Control public;
            }

            location ~ \.php$ {
                    proxy_pass http://127.0.0.1:8080;


                    # Set header to be what we requested
                    proxy_set_header        Host    $host;
                    # Set proxy_cache expiry time
                    proxy_cache_valid  200 302  5m;
                    proxy_cache_valid  404      1m;
                    proxy_cache_valid  301      1h;
                    # Need this for snooping with tcpdump (turns off upstream compression)
                    proxy_set_header        Accept-Encoding  "";
                    # Set real IP header (needed for client IP detection in apache)

                    proxy_set_header  X-Real-IP  $remote_addr;
                    # Explicitly allow critical headers
                    proxy_pass_header Set-Cookie;
                    # Prevent 304 responses being returned from Apache and cached by nginx
                    proxy_set_header If-None-Match "";
            }

            location ~ /\.ht {
                    deny all;
            }

    }