Keeping state on the server

I understand that this a server-based question, but it’s much more suited to Flex developers who have server-side programming experience. The thread does belong here.

I am in the process of writing a Flex AIR application which is quite large and complex and as such I am using the Cairngorm framework to organise the application. So far, it’s working quite nicely.

I am using RemoteObject requests to the server (using Zend_AMF on PHP) to get and receive data from the client. This is also what I’m using for the login method, where I send a partially filled UserVO (username and password are the only fields set) value-object and it returns a full UserVO if the login is valid and null if the login is invalid. This is working fine.

The problem comes in storing the information between requests. I initially set about using sessions (Zend_Session implementation) but the sessions don’t seem to be maintained between requests whether I use cookies or not.

Can sessions be used in RemoteObject service requests? How? If not, what can I use?

I understand that RemoteObject instances have setCredentials functions but I can’t seem to find much about how these work in the back-end.