Passing data between different sites (on different servers)

Question

I have 5 different websites on 5 different servers, I am now attempting to create 1 login system for them all, i use php for the session handling on all of them, but now i need to pass sessions between sites/server securely, please advice me to the best way to achieve this.

Answer 1

But do you have a common user database? You can store the session id and username with cookies and read it in the other websites, but you need to share the session information across all servers using some comunication method. Just create some webservices to validate login in one of them.

Answer 2

This is called Single Sign-On .