I don't know Yii nor how you are using it to implement your login system, but I've never had any problem using other frameworks (e.g. CodeIgniter and the custom framework we use at work) in implementing multi-level login systems (e.g. regular users, moderators, and admins). A typical approach is to add a column to the users table in the DB used to indicate each user's type (e.g. 1 = normal user, 2 = moderator, 3 = admin), and you add conditional logic as needed to control what levels have access to which pages/data.