PHP password_hash and password_verify Tutorial: Secure Registration and Login with PDO and MySQL
Almost every PHP project needs a login page: a capstone system, an inventory app, a school portal, an admin panel. And almost every beginner tutorial from ten years ago still saves passwords with md5(). That is the one part of a login system you really cannot get wrong, because if your database ever leaks, weak password hashes turn into real passwords within minutes.