In a quick post to his site Sameer Borate looks more in-depth at how MVC routers work to translate the incoming request and point it to the right code for handling.

A MVC Router class or a Dispatcher inspects the URL of an HTTP request and attempts to match individual URL components to a Controller and a method defined in that controller, passing along any arguments to the method defined.

He provides the code for a simple example, matching the path directly from $_SERVER['PATH_INFO'] to a key name in a set of routes. Routes are added to the list via an add_routes method and are only matched directly. This is the most basic version of a router with many other frameworks stacking features on top including wildcard matching, optional parameters and regular expression matching.