I have a server set up with nginx and PHP-FPM, running a framework that essentially sends all requests for content to PHP, which then serves it based on ACL rules. This includes images and other static content.

What I am trying to figure out is how I can get nginx to cache such objects to avoid the call to PHP for identical data, ie. a static image that hasn't changed.

Since all these calls are essentially dynamic, and often the image objects won't have easily identifiable extensions, I'm not sure how I might go about caching them.

I could put Varnish in front of nginx and have it do the caching but that would not allow caching of HTTPS traffic.

Suggestions welcome!