This article mainly shares with you the detailed explanation of Yii installation and application. First, install Yii. You can install Yii in two ways: using Composer or downloading an archive file.
It is recommended to use the former, so that you can install new extensions or update Yii by executing a simple command.

After the standard installation of Yii, both the framework and a project template are downloaded and installed.
A project template is a viable Yii project that implements some basic features, such as login, contact form, etc.
Its code is organized in a recommended way. Therefore, it can be suitable as a good starting point for your project.

Installing through Composer

Installing Composer

If Composer has not been installed, you can install it according to the method in getcomposer.org.
In Linux and Mac OS X you can run the following command:

curl -sS https://getcomposer.org/installer | php mv composer.phar /usr/local/bin/composer

In Windows, you need to download and run Composer-Setup.exe.

If you encounter any problems or want to learn Composer in more depth, please refer to the Composer documentation (English),
Composer Chinese.

If you have already installed Composer, please make sure you are using the latest version.
You can use thecomposer self-updatecommand to update Composer to the latest version.

After Composer is installed, switch to a directory accessible through the Web and execute the following command to install Yii:

composer global require "fxp/composer-asset-plugin:^1.3.1" composer create-project --prefer-dist yiisoft/yii2-app-basic basic

The first command installs the Composer asset plugin,
It is through Composer is necessary to manage bower and npm packages. This command takes effect globally and can be used once and for all.
The second command will install Yii in a directory namedbasic. If you want to use a different directory name, you can choose a different directory name.

Note: Composer may ask you for GitHub account authentication information during the installation process, because the GitHub API (for anonymous users) usage limit may be exceeded during use. Because Composer needs to download all extension packages from GitHub
A large amount of information is obtained from , so it is normal to exceed the limit. (Annotation: It also means that as a programmer, you really can’t have fun without a GitHub account.) After logging in to GitHub, you can get a higher API limit so that Composer can run normally. For more details, please refer to Composer
Documentation (This section of the Composer Chinese documentation looks forward to your participation).

Tips: If you want to install the latest development version of Yii, you can use the following command instead,
It adds a stability option (Chinese version):

composer create-project --prefer-dist --stability=dev yiisoft/yii2-app-basic basic

Copy after login

Note that the development version (dev version) of Yii should not be used in a production environment, as it may damage running code.

Installation through archive file

Installing Yii through archive file consists of three steps:

1. Download the archive file from yiiframework.com.

2. Extract the downloaded file to a web-accessible folder.

3. Modify theconfig/web.phpfile and add a key to thecookieValidationKeyconfiguration item
   (if you installed it through Composer, Then this step will be completed automatically):

   // !!! 在下面插入一段密钥（若为空） - 以供 cookie validation 的需要'cookieValidationKey' => '在此处输入你的密钥',

   Copy after login

Run the application

After installing Yii, there will be a runnable Yii application.
Depending on the configuration , can be accessed throughhttp://hostname/basic/web/index.phporhttp://hostname/index.php.

Application structure

The most important directories and files in the application (assuming the application root directory isbasic):

basic/ 应用根目录 composer.json Composer 配置文件, 描述包信息 config/ 包含应用配置及其它配置 console.php 控制台应用配置信息 web.php Web 应用配置信息 commands/ 包含控制台命令类 controllers/ 包含控制器类 models/ 包含模型类 runtime/ 包含 Yii 在运行时生成的文件，例如日志和缓存文件 vendor/ 包含已经安装的 Composer 包，包括 Yii 框架自身 views/ 包含视图文件 web/ Web 应用根目录，包含 Web 入口文件 assets/ 包含 Yii 发布的资源文件（javascript 和 css） index.php 应用入口文件 yii Yii 控制台命令执行脚本

Generally speaking, in the application The files can be divided into two categories: those underbasic/weband those under other directories.
The former can be accessed directly through HTTP (such as a browser), while the latter cannot and should not be accessed directly.

Request life cycle

The following diagram shows how an application handles requests:

1. The user submits the request to the entry scriptweb/index.phpInitiate a request.

2. The entry script loads the application configuration and creates an application
   instance to handle the request.

3. The application resolves the requested
   route through the request component.

4. The application creates a controller instance to handle the request.

5. The controller creates an action instance and executes the filter against the action.

6. If any filter returns failure, the action is cancelled.

7. If all filters pass, the action will be executed.

8. The action loads a data model, perhaps from a database.

9. The action renders a view and provides the data model to it.

10. The rendering result is returned to the response component.

11. The response component sends the rendering result to the user's browser.

Related recommendations:

Yii introductory tutorial - Yii installation and hello world

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