These days, you don't always need to worry about creating user accounts; you can simply use an external service instead, and let the user connect their third-party or social account with your application.
Popular services such as Facebook, Google, and Twitter all provide an API to define and connect a new application. Focusing on Facebook, their services rely on OAuth for a token-based authorization system. OAuth is an open protocol for authentication and authorization; it allows you to use a third-party service to identify a user without directly accessing their credentials (password).
In this recipe, we'll be using Opauth to connect our CakePHP application with Facebook.