Use this PHP library to interface with the App.net's Stream social networking API. Access application functions like: social graph, messaging, and places. Documentation, including code examples and access to other libraries is available on the library's GitHub page. Note that the API is in development and the library continues to be updated. The developers note that some updates may break backward compatibility for older versions.
User authentication in apps is a pain, even if you've built an authentication system dozens of times. Forms, sessions, user tables, validation, password management, the list goes on in the seemingly never-ending to-do list for setting up a simple signup, login, and logout system for your app. OpenID company Janrain makes it easier, building on top of social networks.