cache class

Hi, I'm having a bit of a problem. I include a class in my script, the first time run fine, and then if I change anything in my class, changes are not reflected on the browser, it's like it's still the old class which is used. I've cleared the browser cache, force a pragma no-cache, but no, nothing do the trick. even if I do "return;" at the beginning of the method I called, it doesn't work... does someone have a clue about what is going on ?