Marco Tabini has posted his list of what he considers five features of PHP5 that you "can't afford to ignore" when doing your development work:

Despite the fact that you may not have a choice in the matter, upgrading comes with a number of bonus new features that can help you write better code and gain access to new functionality that required a fair amount of hacking in previous version. Here's a quick list of 5 personal favourites.

The feature to make his list are SimpleXML, JSON/SOAP, PDO, the Standard PHP Library and SQLite. Each has their own bonus feature(s) included too for a little extra incentive to check them out.

DevShed has started up a new tutorial series today with part one of their overview of the DOM extension that's included with PHP5:

Simply put, the DOM XML extension, as its name suggests, will permit you to work on XML documents by way of the DOM API. [...] In this article series I'll be discussing some of its most relevant methods and properties and accompanying all of these explanations with concise and instructive hands-on examples.

They look at using the DOM to create new documents, modify documents by adding additional nodes and converting over a SimpleXML document to be manipulated.