On the PHPBuilder.com site today there's a new tutorial posted from Octavia Anghel about creating a login for your site that's powered by Ajax and uses a bit more security than normal. It includes hooks to use the Ajax Server Secure Layer or an OpenSSL connection.
In this article you will learn how to write a login application in PHP using Ajax and SSL/TLS in two ways either using aSSL (Ajax Server Secure Layer), a library that implements a technology similar to SSL without HTTPS or a simple Ajax and OpenSSL, an open source implementation of the SSL and TLS protocols.
They start with the aSSL method and link you to a download of the tool as well as some sample code to help you get started passing data to it via the session. The second example shows the OpenSSL method, mostly consisting of checking on the server side of the certificate that's passed along with the request.