On DevArticles today, they have posted the last part of their "Building a CHAP Login System" series - An Object-Oriented Approach.

Welcome to the last part of the series "Building a CHAP login system." In three parts, this tutorial provides the basics for building secure login forms, by utilizing the Challenge Handshake Authentication Protocol (known popularly as CHAP). The programming foundation of the system resides primarily on the implementation of the cryptographic MD5 hashing algorithm in JavaScript for sending out encrypted data to the server, which in turn authenticates the client.

In this final part of the series, I shall do two things. First, I will provide a quick overview of the CHAP login system I developed. Second, I’ll focus on the makings of a PHP class for encapsulating all the required processing for generating random seeds and managing session variables. The starting point for building the wrapping class will be the procedural script that you saw in the previous part of the series.

They take the previously procedural code and transfer it over to (in my opinion) a much simpler layout - and one that's easier to use/extend.