Google Apps as single authentication point for your corporate applications

This is an update to my post "Google Apps Premier federated login with PHP". Idea is simple, users do not like passwords, less passwords - less pain and more security.

Nowadays many companies have gone cloud, which covers most needs, but leaves space for homegrown small applications, ideas, prototypes, etc. It is convenient to organize user login into these applications using already existing Google Apps login infrastructure.

This is about using it with PHP.