I’ve just finished a wiki article named “Drills : Search by a HAS_MANY relation in Yii 2.0”
http://www.yiiframework.com/wiki/780/drills-search-by-a-has_many-relation-in-yii-2-0/
It is an update to the wiki "Drills : Search by a HAS_MANY relation in Yii 1.1"
http://www.yiiframework.com/wiki/428/drills-search-by-a-has_many-relation-in-yii-1-1/
The latter has been one of my best writings so far, and I hope it has helped people a bit. 
Now, we have Yii 2.0. I tried to solve the same tasks using ActiveRecord of Yii 2 as I did using CActiveRecord of Yii 1.1. The differences are, believe me, fantastic!!
Corrections to the article are always welcome. 