Magento Module PHP Caching? Or Server Caching PHP?

Does Magento cache the php of a module installed?

I have an export to CSV module that I've modified in a number of ways with no results at all. Finally I deleted the content of the main part of the module that writes the (Csv.php) and in admin I can still export to CSV?

So does magento cache modules or the php of modules anywhere, and if so how can I clear it / reset the module for my modifications?

Thanks.

EDIT: I've made the same changes on a local host version of Magento and got the results I was after. So secondary question is if Magento doesn't - would my server be caching the PHP?

Solution

Yes. Go to System > Tools > Compilation and click the Disable button.

Take 2: Files in app/code/core/ can be overridden in app/code/community/ and likewise by app/code/local. If you edit a file in core that is present in one of the other directories then your edit has no effect.

Take 3: If you have APC or XCache installed on your server then it might not have noticed a changing file. Restart the apache or php-cgi process.