What does Yii::app() mean?

Yii::app() is an instantiated object, an object that we can directly operate in the current framework. We can understand this object as a request application first object.

Yii framework is a pure OOP object-oriented framework, which uses objects to call attributes and methods of classes to complete application requests. (Recommended learning: yii tutorial)

Through the analysis of the above figure, we know that Yii::app() is the first in the system The object is the boss. We can use this object to call other related methods, properties, and objects in the system.

Yii::app() is an object instantiated by the CwebApplication class

CwebApplication(framework/web/CwebApplication.php)

Therefore, Yii::app() can call related properties or methods in CwebApplication or the parent class CApplication.

Note: Do not access related methods of CwebApplication or its parent class casually, as it will affect system stability.

System application components

We can call system components through Yii::app()

User session request log db, etc.

In the system The above components can be directly accessed from any corner

Yii ::app()->user  (实例化对象'CWebUser' => '/web/auth/CWebUser.php',)
Yii ::app()->session(实例化'CHttpSession')
Yii ::app()->request
Yii ::app()->db

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