On PHPMaster.com today there's a new tutorial showing you how to create a simple RESTful API with the help of the Slim PHP microframework.

Through a series of articles here at PHPMaster you’ve learned about what is REST and how it works. In this article, I’d like to show you how to create a RESTful web service using Slim, a PHP micro-framework inspired by Sinatra, a Ruby framework. It’s well-suited for creating simple RESTful web services and comes with some minimal components like Router, Request, Response, and View. It’s very simple, and is easy to understand and use.

He walks you through the basics of getting the framework downloaded and set up as well as showing you how to make some basic routes ("Hello World" style). He then uses the NotORM library to work with his database and, via a RESTful interface, give information about books, edit their information and add new ones.