Sentry is an open source PHP 5.3+ fully-featured authentication & authorization system. It also provides additional features such as user groups and security features. It's framework agnostic (composer), so it can be installed on Laravel, CodeIgniter, etc. They recently released their official docs and I really like how the interface works. Related discussion: http://www.reddit.com/r/PHP/comments/1aitay/simple_powerful_and_easy_to_use_authorization_and/