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
and the Web server handles the request by executing the bootstrap script
urlManager. For this example, the controller
post which refers to the
PostController class; and the action is
whose actual meaning is determined by the controller.
show refers to a method named
actionShow in 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.
Post model whose ID is
1 from the database.
show with the