Nginx反向代理如何只缓存静态文件 不缓存php脚本文件？

Question

下面是Nginx配置
怎么写才能实现只缓存js css jpg等静态文件
不缓存php等脚本

还有Nginx反代是不是没办法转发源文件的Content-Type？

感谢

server {
    listen 80; #listen end
    server_name xx.com; #server_name end
    index index.html index.htm index.php; #index end

    root  /home/wwwroot/xx/domain/xx/web; #root end
    include /home/wwwroot/xx/rewrite/con.conf; #rewrite end

    proxy_cache xx; #proxy_cache end
    proxy_temp_path /home/wwwroot/xx/cache_temp;
    proxy_cache_key $scheme://$host$request_uri;
    proxy_cache_valid 200 304 12h; #cache_valid end
    proxy_connect_timeout 60s; #connect_timeout end


    location / {
        default_type text/html;
        subs_filter_types text/css text/xml; #subs_filtert end
        proxy_set_header X-Real-IP  $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Referer http://cc.com; #header_referer end
        proxy_set_header Host cc.com; #header_host end
        proxy_pass http://cc.com; #proxy_pass end
        proxy_set_header Accept-Encoding "";
    }

    access_log off; #access_log end
    error_log /dev/null; #error_log end
}