Yii::app()->User->Setstate In Yii Working

I want to know about this in yii:

Yii::app()->user->setState(‘key’,‘value’);

If I have a array of size 10 and I set this array in state like:

 Yii::app()->user->setState('data',$dataArray) 

I have another array of size 15000 and I set this array in state like:

 Yii::app()->user->setState('data',$dataArray)

Is this Ok?

Or It will effect the speed of my Yii project i.e. larger the setState data size ,slower will be the speed of yii project?

Is it is secure way for confidential data like Password to set in Yii::app()->user->setState(‘password’,$password)?

Thanks

sessions are for small state

>> Yii::app()->user->setState(‘data’,$dataArray) // 15000

save it in the database

>> Is it is secure way for confidential data like Password to set in Yii::app()->user->setState(‘password’,$password)?

not a good idea I would not recomend