Matthew Weier O'Phinney has posted a "second part" of a group of articles he's doing on web services with the Zend Framework. In this new blog post he gets into more detail on setting up REST interfaces for your applications.

At its heart, REST simply dictates that a given resource have a unique address, and that you interact with that resource using HTTP verbs. [...] What the REST paradigm provides you is a simple, standard way to structure your CRUD (Create-Read-Update-Delete) applications. Due to the large number of REST clients available, it also means that if you follow the rules, you get a ton of interoperability with those clients.

He shows how to create a simple REST server with the Zend_Rest_Route package and touches briefly on the proper way for your script to respond to a request.