CiviCRM Community Forums (archive)

I'm trying to track down what I think might be a bug, but am having trouble even figuring out where to start because I can't figure out how CiviCRM steps into the code, or what the first function / method is that's called when processing a form (in this case, the form on the contribution confirmation page, but it's something I've had trouble with in other cases too).  I've poked around the documentation a bit, but all I can find is a link to an "architecture" page that no longer exists.  Any tips on where to start?

Thanks!

EDIT:  It looks like everything runs through the "state machine".  Not sure how we get to that point or how the parameters are extracted from request data, etc, but don't really need to know that just now.