Session's across Domains...

I have a server with a few virtual hosts. All of my scripts use "session_start()", and $_SESSION[] to share data between invocations of different scripts. The problem I'm having is that if a form on site A submits to a script on site B the values stashed in $_SESSION[] appear to be lost... Should this work? If not, then what alternatives exist? I suppose I could pass the session id as a POST argument to the site B script (and theirs probably a method in PHP that given a session_id() makes available all of that sessions $_SESSION[] variables) but is that the best way? td -- for only the most hard core geekstas... http://geekstasparadise.blogspot.com