I'm trying to implement user login part of my website. I thought it would be much easier just to use a library rather than write a 1000 lines of code to reinvent the wheel. So I'm just trying to get stackoverflow's opinion, what is the best php user login authentication library out there. I've been looking around (usercake, kohana) but a lot of them look like a high-school project by someone rather than a fully supported and developed library. Also, they seem to be using the deprecated mysql injections and I want to use PDO.
Try PEAROpenID package.
Check the other PEARAuthentication packages too.