Allow PHP to delete Nginx cache files

Hello!

I’m using the Nginx FastCGI cache on Debian 7 and I’d like to allow PHP to delete Nginx’s cache files.

PHP-FPM runs as www-data. Nginx runs as nginx.

/var/cache/nginx owner and group is root, permissions are 755 (drwxr-xr-x).

Directories in /var/cache/nginx are owned by nginx, group is root, permissions are 700 (rwx------). Files in /var/cache/nginx owner and group is nginx, permissions are 600 (rw-------).

How can permanently allow the user www-data to delete files in /var/cache/nginx?

I have minimal knowledge about unix user/groups or filesystem ACL’s, any leads appreciated!