How to diagnose APC caching issue?

Question

I recently turned on APC on a site which uses the Rackspace Cloudfiles PHP API library. Yesterday, the uploading process to Cloudfiles failed which I believe is due to an expired token that is being cached by APC. Is there a way to diagnose this issue or should I just prevent all the cloudfiles library code from being cached with the apc.filters configuration?

Edit: I suspected that APC caching was the issue because I updated a relevant file by only adding a single line of code that logged the token. After updating the file, the uploading process started to work again.

Edit2: This was occurring in a background script that is constantly running. The value was being stored in the script and not being updated. I forgot that I had restarted the script after making the change which allowed the token to be updated.

Answer 1

On its own, APC only caches the compiled contents of PHP source files -- it would not (and could not!) cache an API token. Your problem probably lies elsewhere.