Ajax and XML: Use Ajax Techniques to Create Input Forms

Augmenting your HTML forms with Asynchronous JavaScript + XML (Ajax)
callbacks to the server is a practical way to add Web 2.0 functionality
to your application. When you think about Web 2.0 applications, often
the most glamorous of them come to mind: the video of YouTube, the
über-cool scrolling map of Google Maps, the geo-location functionality
in Flikr. Often overlooked in such sites, however, is the humble HTML
form that has undergone a big transformation with the popularization of
Ajax technology. In this article, I show you how to use the Prototype.js
JavaScript library to solve common user experience problems as you
augment forms with Ajax code. You will discover a variety of techniques
to add Ajax code and enhance the user experience for PHP applications.