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114 lines
4.0 KiB
114 lines
4.0 KiB
6 years ago
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Entry Scripts
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=============
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Entry scripts are the first step in the application bootstrapping process. An application (either
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Web application or console application) has a single entry script. End users make requests to
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entry scripts which instantiate application instances and forward the requests to them.
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Entry scripts for Web applications must be stored under Web accessible directories so that they
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can be accessed by end users. They are often named as `index.php`, but can also use any other names,
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provided Web servers can locate them.
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Entry scripts for console applications are usually stored under the [base path](structure-applications.md)
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of applications and are named as `yii` (with the `.php` suffix). They should be made executable
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so that users can run console applications through the command `./yii <route> [arguments] [options]`.
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Entry scripts mainly do the following work:
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* Define global constants;
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* Register [Composer autoloader](https://getcomposer.org/doc/01-basic-usage.md#autoloading);
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* Include the [[Yii]] class file;
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* Load application configuration;
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* Create and configure an [application](structure-applications.md) instance;
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* Call [[yii\base\Application::run()]] to process the incoming request.
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## Web Applications <span id="web-applications"></span>
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The following is the code in the entry script for the [Basic Web Project Template](start-installation.md).
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```php
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<?php
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defined('YII_DEBUG') or define('YII_DEBUG', true);
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defined('YII_ENV') or define('YII_ENV', 'dev');
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// register Composer autoloader
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require __DIR__ . '/../vendor/autoload.php';
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// include Yii class file
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require __DIR__ . '/../vendor/yiisoft/yii2/Yii.php';
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// load application configuration
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$config = require __DIR__ . '/../config/web.php';
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// create, configure and run application
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(new yii\web\Application($config))->run();
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```
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## Console Applications <span id="console-applications"></span>
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Similarly, the following is the code for the entry script of a console application:
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```php
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#!/usr/bin/env php
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<?php
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/**
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* Yii console bootstrap file.
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*
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* @link http://www.yiiframework.com/
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* @copyright Copyright (c) 2008 Yii Software LLC
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* @license http://www.yiiframework.com/license/
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*/
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defined('YII_DEBUG') or define('YII_DEBUG', true);
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defined('YII_ENV') or define('YII_ENV', 'dev');
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// register Composer autoloader
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require __DIR__ . '/vendor/autoload.php';
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// include Yii class file
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require __DIR__ . '/vendor/yiisoft/yii2/Yii.php';
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// load application configuration
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$config = require __DIR__ . '/config/console.php';
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$application = new yii\console\Application($config);
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$exitCode = $application->run();
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exit($exitCode);
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```
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## Defining Constants <span id="defining-constants"></span>
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Entry scripts are the best place for defining global constants. Yii supports the following three constants:
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* `YII_DEBUG`: specifies whether the application is running in debug mode. When in debug mode, an application
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will keep more log information, and will reveal detailed error call stacks if exceptions are thrown. For this
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reason, debug mode should be used mainly during development. The default value of `YII_DEBUG` is `false`.
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* `YII_ENV`: specifies which environment the application is running in. This will be described in
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more detail in the [Configurations](concept-configurations.md#environment-constants) section.
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The default value of `YII_ENV` is `'prod'`, meaning the application is running in production environment.
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* `YII_ENABLE_ERROR_HANDLER`: specifies whether to enable the error handler provided by Yii. The default
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value of this constant is `true`.
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When defining a constant, we often use the code like the following:
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```php
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defined('YII_DEBUG') or define('YII_DEBUG', true);
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```
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which is equivalent to the following code:
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```php
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if (!defined('YII_DEBUG')) {
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define('YII_DEBUG', true);
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}
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```
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Clearly the former is more succinct and easier to understand.
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Constant definitions should be done at the very beginning of an entry script so that they can take effect
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when other PHP files are being included.
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