syntax to access an index of the session variable directly?

[eluser]stormbytes[/eluser]
Looking for the lazy way out...

Assuming 'user' is an array stored in the session via $this->session->set_userdata('user');

Assuming $user has an index 'id', which would normally be accessed via $user['id']

Is there a way to structure a call to the session that would retrieve only the 'id' index?

Tried $this->session->userdata('user')['id']; which didn't work out too well