With PHP 5.3 coming up on the horizon, I'm of course looking forward to using namespaces.

He gives an example of how useful these namespaces can be for you and your code, but points out one failing point - trying to define classes in a namespace that are named the same as a built-in keyword for PHP. There's already been a suggestion to add a captial "I" in front of the class name to prevent this collision.

There's also the problem of throwing custom exceptions - unless you use the namespace properly your script will just throw a default exception.

The YouTube video sharing site allows Web application developers to access public content through its REST-based developer API. [...] This article introduces the YouTube Data API, demonstrates how you can use it to browse user-generated video content; access video metadata, comments and responses; and perform keyword searches.

They help you get started by outlining the format that the YouTube messages use (Atom feeds) and how to run a query against the API and return back the custom data for things like video categories, popularity and the results of keyword searches.