UserSpice4
An Open Source PHP User and Page Management System
UserSpice is a simple PHP OOP PDO User Management system that gives you everything you need to manage logins, registrations, passwords, and page security. It's dead simple and feature rich.
It also gives you access to fully developed classes for managing your database, users, tokens, cookies, sanitizing inputs and much more.
It's fully documented at UserSpice com and well supported in the forums.