Ben bir sığınakta web hizmeti (PHP) oluşturmak planlıyorum.

api/user
api/user/[id]
api/ad
api/ad/[id];
etc

are "user" and "ad" actual php files? and if not how can i tell (on my php file) which one the caller is calling "user" or "ad"? any good tutorial on how to create a restful web service? Most tutorials only cover the basics of rest web services.