phprbac
PHP Role Based Access Control library
RBAC (role based access control) is the de-facto standard in authorization and access control, because its much easier to maintain and use than traditional ACLs.
Unfortunately due to its complicated internals, not many implementations are available. PHP RBAC is compatible with NIST Level 2 RBAC standard and provides even more, with best performance yet available for any authorization library, and its for PHP.
Note: Development and support has been moved to Github...