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.
JWT is short for JSON Web Token. It is used eg. instead of sessions to maintain a login in a browser that is talking to an API - since browser sessions are vulnerable to CSRF security issues. JWT is also less complicated than setting up an OAuth authentication mechanism.
This article tries to describe the practical techniques of searching by a HAS_MANY relation using ActiveRecord of Yii 2.0.
Here is a step by step To-Do list for Yii beginners. The list is an advice of what tutorials and documentation you can walk through to get a full understanding of the Yii Framework. These can be a help to learn Yii.