Commit e55f8196 by Qiang Xue

updated the lifecycle chart. [skip ci]

parent 69828422
......@@ -14,7 +14,7 @@ and how the application handles requests in general.
Functionalities
---------------
The application that you have installed has four pages:
The application that you have installed contains four pages:
* the homepage is the page displayed when you access the URL `http://hostname/index.php`;
* the "About" page;
......@@ -54,45 +54,42 @@ basic/ application base path
```
In general, the files in the application can be divided into two parts: those under `basic/web` and those
under other directories. The former can be directly accessed from Web, while the latter can/should not.
under other directories. The former can be directly accessed from Web, while the latter can not and should not.
Your application uses a single entry `web/index.php`. It is the only PHP script that is directly accessible from Web.
It takes ALL Web requests, creates an [application](structure-applications.md) instance to handle the requests,
and then sends back the responses.
Yii implements the [model-view-controller (MVC)](http://wikipedia.org/wiki/Model-view-controller) design pattern,
as reflected in the above directory organization. The `models` directory contains all [model classes](structure-models.md),
Yii implements the [model-view-controller (MVC)](http://wikipedia.org/wiki/Model-view-controller) design pattern
which is reflected in the above directory organization. The `models` directory contains all [model classes](structure-models.md),
the `views` directory contains all [view scripts](structure-views.md), and the `controllers` directory contains
all [controller classes](structure-controllers.md).
The following diagram shows the static structure of an application:
The following diagram shows the static structure of an application.
![Static Structure of Application](images/application-structure.png)
![Static structure of Yii application](images/application-structure.png)
Each application has an entry script `web/index.php` which is the only Web accessible PHP script in the application.
The entry script takes an incoming request and creates an [application](structure-applications.md) instance to handle it.
The [application](structure-applications.md) resolves the request with the help of its [components](concept-components.md)
and dispatches the request to MVC. [Widgets](structure-widgets.md) are used in the [views](structure-views.md)
to help build complex and dynamic user interface elements.
Request Lifecycle
-----------------
The following diagram shows a typical workflow of a Yii application handling a user request:
![Typical workflow of a Yii application](images/application-lifecycle.png)
1. A user makes a request of the URL `http://www.example.com/index.php?r=post/show&id=1`.
The Web server handles the request by executing the bootstrap script `index.php`.
2. The bootstrap script creates an [[yii\web\Application|Application]] instance and runs it.
3. The Application instance obtains the detailed user request information from an application component named `request`.
4. The application determines which [controller](controller.md) and which action of that controller was requested.
This is accomplished with the help of an application component named `urlManager`.
For this example, the controller is `post`, which refers to the `PostController` class, and the action is `show`,
whose actual meaning is determined by the controller.
5. The application creates an instance of the requested controller to further handle the user's request.
The controller determines that the action `show` refers to a method named `actionShow` in the controller class.
The controller then creates and executes any filters associated with this action (e.g. access control or benchmarking).
The action is then executed, if execution is allowed by the filters (e.g., if the user has permission to execute that action).
6. The action creates a `Post` [model](model.md) instance, using the underlying database table, where the ID value of the corresponding record is `1`.
7. The action renders a [view](view.md) named `show`, providing to the view the `Post` model instance.
8. The view reads the attributes of the `Post` model instance and displays the values of those attributes.
9. The view executes some [widgets](view.md#widgets).
10. The view rendering result--the output from the previous steps--is embedded within a [layout](view.md#layout) to create a complete HTML page.
11. The action completes the view rendering and displays the result to the user.
The following diagram shows how an application handles a request.
![Request Lifecycle](images/application-lifecycle.png)
1. A user makes a request to the [entry script](structure-entry-scripts.md) `web/index.php`.
2. The entry script loads the application [configuration](concept-configurations.md) and creates
an [application](structure-applications.md) instance to handle the request.
3. The application resolves the requested [route](runtime-routing.md) with the help of
the [request](runtime-requests.md) application component.
4. The application creates a [controller](structure-controllers.md) instance to handle the request.
5. The controller creates an [action](structure-controllers.md) instance and performs the filters for the action.
6. If any filter fails, the action is cancelled.
7. If all filters pass, the action is being executed.
8. The action loads a data model, possibly from a database.
9. The action renders a view with the data model.
10. The rendering result is to the [response](runtime-responses.md) application component.
11. The response component sends the rendering result to the user.
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