We are going to deploy the new yiiframework.com website on March 23, 2018 from 8:00 to 12:00 UTC.
Website and Yii documentation will not be available in this time frame. Check the news for more details.
The Definitive Guide introduces the fundamentals of managing URLs in a Yii application. In this tutorial, we introduce a practical technique that can quickly turn your application into using search-engine-friendly URLs.
I have read http://www.yiiframework.com/wiki/24/creating-a-dependent-dropdown/ (Dependen Dropdown Yii1), but I can't implement it in Yii2 because Yii2 does not have built-in AJAX functionality hem.. I searched about it and came across this post