security - Adding User Authentication in PHP -

Now I know that I should not try to change the wheel again and try to write the authentication system, Because I do not understand the security issues are well enough though, I need to add a basic authentication system to my site, so I can limit access to some resources.

How do you suggest that I do this?

EDIT: I am not trying to make myself a certification system, I am looking for libraries which I can use to integrate certification in my website.

I have structures like KPPHP and CI to help you with a lot of box tool which you Developers can use a large community.

But, if your own system attempts to do a Google search after flipping your own authentication system, then there are tones out there for resellers like:

Many of its ...