Preventing multiple submits

Hi folks, I'm still working on my first PHP project and was wondering how to prevent users from submitting the same form multiple times when they continually click on the submit button. I've heard it's possible to prevent this with Javascript but is it also possible to use PHP (encase the user doesn't have Javascript enabled, etc)? I assume you could assign a temporary variable and increment it when the submit button is pressed and then check against that? Would that work? I'm sure people have already solved this problem? Thanks James