Login system

I've been working this week on trying to figure out how to register users and log them into my site. This tutorial has been really helpful to me and might be for you if you want to do the same thing:
http://net.tutsplus.com/articles/news/how-to-build-a-login-system-for-a-simple-website/
The only problem is it doesn't finish- it doesn't show you how to register users or set an expiration date to the session. But it has enough for it to make sense to me and do the rest on my own.
Good luck!