We have a current (legacy) PHP based website that is unlikely to be redeveloped for the next year or so, that acts as our main portal.
We would like to develop new applications in ASP.Net, and plug them into the current portal – but we do not want our website users to have to log in twice.
Whats the best way to share authentication state between the two platforms? They do not share the same server, database backend or even proxy.
Read this article from Microsoft on sharing session state between classic ASP and ASP.NET:
http://msdn.microsoft.com/en-us/library/aa479313.aspx
Conceptually, I think this is pretty similar to what you’re trying to do, though I don’t know just how helpful the above document will be to your specific case. Definitely worth a look though.