Why is session name different than what I set

[eluser]skalrynd[/eluser]
You are correct in that PHPSESSID is typically the default cookie name.

Generally PHPSESSID's value is the session ID issued by php. It is odd that the cookie is being set but with an empty value. But then that could be why you are not seeing it in IE.

Some servers are set to automatically issue a session id in the page header. I believe it's a configuration in the ini (session.auto_start)

Check your server's session directives and compare here:

http://us2.php.net/manual/en/session.configuration.php

If the behavior in FF is correct as you mentioned above and it's based on functionality like CI_Session:ess_read() in order to determine whether or not a user is logged in, then obviously the cookie 'ci_session' is being written. Some value is being returned to be used in the logic.

Most importantly If you DO have a ci_session cookie getting defined, PHPSESSID is a red herring for you unless you're wanting to alter the ini for session handling on your server. Not knowing many other details, I find this possibility most suspect.

Hope this helps.