It's well known that there are Lazy Loading approach and Eager Loading approach in the relational query. But it's very important to know how the Eager Loading approach works in Yii 2. It has changed drastically from that of Yii 1.1, and there are common misunderstandings about it in the community.
I've read many comments that it's not possible to install Yii 2 advanced on a shared hosting environment, as it has two webroots. This is partially true.