Matthew Weier O'Phinney has a new post to his blog looking at using the Zend Framework to create various types of API interfaces - SOAP, XML-RPC, JSON_RPC and AMF.
The hubbub surrounding "Web 2.0" is around sharing data. In the early iterations, the focus was on "mashups" -- consuming existing public APIs in order to mix and match data in unique ways. Now, more often than not, I'm hearing more about exposing services for others to consume. Zend Framework makes this latter trivially easy via its various server classes.
He suggests splitting out the API from the rest of the application, though. The extra overhead caused by the normal MVC process could increase the response time. He proposes a method that moves them out of the main site's root and uses rewrite rules to get things to the correct place (even for multiple request format types). The mod_rewrite example for this is included as well as a bit of sample code showing how the request would work.