The phpaddiction website has posted the first part of a series today covering URL routing with PHP (commonly used by frameworks to route requests through a centralized location.
Most PHP frameworks use some variation of the front controller pattern to centralize common code and logic. There are advantages and disadvantages to this. I am going to ignore those for now. In fact the first part of this series will explore a simple procedural URL routing method that contains many of the disadvantages. In later articles we will build upon this basis and address the disadvantages.
He walks through the steps to get things set up - working with mod_rewrite, creating the "entry point" for your application, and finally, how to execute a command based on the request's action.