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.
Functionality < span id = "functionality" > < / span >
-------------
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 ](tool-debugger.md ) 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 maintainance tasks for the application, which are described
in the [Console Application Section ](tutorial-console.md ).
Application Structure < span id = "application-structure" > < / span >
---------------------
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) ](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.
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 the MVC elements. [Widgets ](structure-widgets.md ) are used in the [views ](structure-views.md )
to help build complex and dynamic user interface elements.
Request Lifecycle < span id = "request-lifecycle" > < / span >
-----------------
The following diagram shows how an application handles a request.
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 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 ](runtime-responses.md ) application component.
11. The response component sends the rendered result to the user's browser.
