Yii implements the model-view-controller (MVC) design pattern which is widely adopted in Web programming. MVC aims to separate business logic from user interface considerations so that developers can more easily change each part without affecting the other. In MVC, the model represents the information (the data) and the business rules; the view contains elements of the user interface such as text, form inputs; and the controller manages the communication between the model and the view.
Besides MVC, Yii also introduces a front-controller, called application, which represents the execution context of request processing. Application resolves the user request and dispatches it to an appropriate controller for further handling.
The following diagram shows the static structure of an Yii application:
Static structure of Yii application
The following diagram shows a typical workflow of an Yii application when it is handling a user request:
A typical workflow of Yii application
http://www.example.com/index.php?r=post/show&id=1and the Web server handles the request by executing the bootstrap script
urlManager. For this example, the controller is
postwhich refers to the
PostControllerclass; and the action is
showwhose actual meaning is determined by the controller.
showrefers to a method named
actionShowin the controller class. It then creates and executes filters (e.g. access control, benchmarking) associated with this action. The action is executed if it is allowed by the filters.
Postmodel whose ID is
1from the database.