Update File Woe (Maybe OT!)

This is not truly a php programming question but a problem I have when programming php on which I was hoping someone would shed some light. When I write php code I generally upload directly to a server via ftp. As I am on a pretty fast adsl line I have never seen toi the need to have a sever setup locally. The problem is that the pages I upload seem to cache and therefore unless I rename the file I have edited on the server (and there request a new file) I do not see the changes I have just made- which is problematic when I am trying new things and changes comer thick and fast. The cache on my browser is set to clear itself on every file request. I also manually clear it. However no matter what I seem to have to rename the the file on the server and request it that way. This is an issue in both IE and NS so it is not a browser specific problem. Likewise I do not see to have this same trouble with html or javascript files- only php. Any ideas? I thought it might be to do with some sort of server side cacheing script? Does anyone have any ideas of a few lines of code I could insert at the top of a file that would overcome this? It is really annoying more than anything Cheers