On PHPBuilder.com today, there's the second part in their "Using XML: A PHP Developer's Primer" series.

In the first part of this series, we took a look at how PHP 5 can be used to manipulate and parse XML files. In this installment, we are going to focus on Ajax, one of the most useful and topical applications of XML.

Initially, we are going to introduce Ajax and learn how to use the XMLHTTP object provided by most modern web browsers to create a live email validation form. Then we will pick up where we left off with the theme of XML and introduce XSLT, which we will use to transform our library XML from the previous article into valid XHTML code.

They jump immediately in, starting with the "what is Ajax?" question to provide a good base. The sample application that they help you build to work up your Ajax skills is an email validation app that checks the user's entry as they're putting it in. Of course, all of the PHP and Javascript code that you'll need is provided.