IBM developerWorks has this new tutorial today walking you through the creation process behind an Ajax RSS reader (with some PHP help).

Of course, all of the code is included, and they explain each step of the way - from the creation of the server-side PHP script (PHP), to the generation of the different feed pages, to the Javascript to create the reader itself. There's a little bit of object-oriented knowhow needed to work with some of the PHP, but it's nothing most developers can't tackle. In the end, they've demonstrated two ways to the same result - using both XML and JSON.