Caching Problems???

Okay, I'm not really sure of the cause of this problem, but it's really annoying. Several of my scripts, once they're processed, continue to return the same results even after I've changed something that should have changed the results. eg, I have a script that counts the number of SWFs in a directory and returns that number. But even after deleting or adding SWFs in the directory, it returns the number of SWFs previous to the change. I empty my browser cache, hit shift-refresh, try it on different computers, all with the same result. My PHP book doesn't discuss a PHP server cache that could be causing the problem. Any suggestions? Nick