Weird caching problem with PHP4/Apache

Having successfully uploaded my PHP4+MySQL site finally to Fatcow (and the MySQL stuff IS there--thanks for the help), I'm now left with making it actually work online. One curious problem: For every page in the site ("*.php4"), I include three parts, a header.inc (common to all), a body.inc (unique to each .php4 file), and a footer.inc (common to all). One of the things the header.inc file does is generate select a background image randomly. Very simple, and it works on my local machine. But as soon as I look at the page online, it seems Fatcow (Apache/Zend?)caches the header.inc file--that is, the results of the php script inside it, which generates the random background. I say this because no matter how many pages I look at, refreshing them, etc., I always get sent the same original background image. Even if I replace now the random background image function in header.inc with the explicit name of a different file, it STILL displays the same one. Weird? Is there some way to ensure that each PHP4 file/script is interpreted every single time, and not cached (as it seems)?? ...Rene