for creating yii session
 
Yii::app()->session['userid'] = "value";
You can get value like this
 
$sleep = Yii::app()->session['userid'];
And unset session like
 
unset(Yii::app()->session['userid']); # Remove the session
In case of user signs out , you have to remove all the session.
 
Yii::app()->session->clear();
After this, you need to remove actual data from server
 
Yii::app()->session->destroy();