Problem with IE7 caching

I have a problem with IE7. It has a tendency to cache output produced by PHP. It occurs in a few ways: * I make a minor change to a php program, but you can't see it in

     IE7, but can in FF.  CTRL-Refresh does not make it work.

* I modify data using a form in IE7. When I click on a link to

     return to the form the old data is still there, but if I hit
     CTRL-Refresh the new values are there.

I have set up some caching to try to fix the second issue, but I'm not sure if I've chosen the right header lines: $now = time (); $prety_lmtime = gmdate ('D, d M Y H:i:s', $now). ' GMT'; $prety_emtime = gmdate ('D, d M Y H:i:s', $now + $interval). ' GMT'; // Backwards Compatibility header ("Last Modified: $prety_lmtime"); header ("Expires: $prety_emtime"); // HTTP/1.1 Support header ("Cache-Control: private, max-age=$interval,s-maxage=0"); I got this code from a book. I don't want to prevent caching completely because I want to be able to go back to the form when there is an error in validation of fields before entering it into the db. But I do want to be able to see the new data after it is entered in the db. Charlene