In Yii2, where is the variable Yii: $ app instantiated?

The most common service locator is an application object. You can use Yii: $ app to access the most common service locator is an application object. You can use \ Yii :: $ app access

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The most common service locator is the application object, which can be accessed through \ Yii: $ app

You can see the source code. If your application is a web application, in index. php
(New yii \ web \ Application ($ config)-> run ();
Call the construction method of the Application, and it inherits fromYii \ base \ ApplicationThe constructor is

Public function _ construct ($ config = []) {Yii: $ app = $ this; $ this-> setInstance ($ this); $ this-> state = self:: STATE_BEGIN; $ this-> preInit ($ config); $ this-> registerErrorHandler ($ config); Component ::__ construct ($ config );}

In the subsequent instantiation process, you can view the source code in order. If you have any questions, please leave a message and check the source code to help you quickly understand the initialization and running process of yiiframework.

This is a magic variable!