Running Applications

After installing Yii, you have a working Yii application that can be accessed via the URL http://hostname/basic/web/index.php or http://hostname/index.php, depending upon your configuration. This section will introduce the application's built-in functionality, how the code is organized, and how the application handles requests in general.

Info: For simplicity, throughout this "Getting Started" tutorial, it's assumed that you have set basic/web as the document root of your Web server, and configured the URL for accessing your application to be http://hostname/index.php or something similar. For your needs, please adjust the URLs in our descriptions accordingly.

Note that unlike framework itself, after project template is installed it's all yours. You're free to add or delete code and overall modify it as you need.

Functionality

The basic application installed contains four pages:

  • the homepage, displayed when you access the URL http://hostname/index.php,
  • the "About" page,
  • the "Contact" page, which displays a contact form that allows end users to contact you via email,
  • and the "Login" page, which displays a login form that can be used to authenticate end users. Try logging in with "admin/admin", and you will find the "Login" main menu item will change to "Logout".

These pages share a common header and footer. The header contains a main menu bar to allow navigation among different pages.

You should also see a toolbar at the bottom of the browser window. This is a useful debugger tool provided by Yii to record and display a lot of debugging information, such as log messages, response statuses, the database queries run, and so on.

Additionally to the web application, there is a console script called yii, which is located in the applications base directory. This script can be used to run background and maintenance tasks for the application, which are described in the Console Application Section.

Application Structure

The most important directories and files in your application are (assuming the application's root directory is basic):

basic/                  application base path
    composer.json       used by Composer, describes package information
    config/             contains application and other configurations
        console.php     the console application configuration
        web.php         the Web application configuration
    commands/           contains console command classes
    controllers/        contains controller classes
    models/             contains model classes
    runtime/            contains files generated by Yii during runtime, such as logs and cache files
    vendor/             contains the installed Composer packages, including the Yii framework itself
    views/              contains view files
    web/                application Web root, contains Web accessible files
        assets/         contains published asset files (javascript and css) by Yii
        index.php       the entry (or bootstrap) script for the application
    yii                 the Yii console command execution script

In general, the files in the application can be divided into two types: those under basic/web and those under other directories. The former can be directly accessed via HTTP (i.e., in a browser), while the latter can not and should not be.

Yii implements the model-view-controller (MVC) architectural pattern, which is reflected in the above directory organization. The models directory contains all model classes, the views directory contains all view scripts, and the controllers directory contains all controller classes.

The following diagram shows the static structure of an application.

Static Structure of Application

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 instance to handle it. The application resolves the request with the help of its components, and dispatches the request to the MVC elements. Widgets are used in the views to help build complex and dynamic user interface elements.

Request Lifecycle

The following diagram shows how an application handles a request.

Request Lifecycle

  1. A user makes a request to the entry script web/index.php.
  2. The entry script loads the application configuration and creates an application instance to handle the request.
  3. The application resolves the requested route with the help of the request application component.
  4. The application creates a controller instance to handle the request.
  5. The controller creates an action 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 executed.
  8. The action loads a data model, possibly from a database.
  9. The action renders a view, providing it with the data model.
  10. The rendered result is returned to the response application component.
  11. The response component sends the rendered result to the user's browser.