It should, therefore, be possible to come up with a generic library to perform these tasks, one which provides developers with a reusable code base and eliminates the need to reinvent the wheel every time they build the user management component of a Web application. This library should be flexible enough to adapt to different needs, powerful enough to satisfy most requirements, and robust enough to meet the performance and scalability requirements of most of the current generation of Web applications.
Which brings me, rather nicely, to patUser.
They take the time to explain what the patUser package is all about, including where to grab the latest copy from. There's a SQL file that comes with the installation to help you get started and will be what the tutorial is based around. They provide a basic example of adding and authenticating a user, breaking it down into chunks to explain it.
They also include a method to make the patUser system use a plain HTTP authentication instead of integrating into a template - sometimes a simpler, quicker approach for validating users.