Courses Yii Tutorial on Yii Entry Scripts

web application (as well as console application) has a single entry script. the end user makes request to the entry script. then the entry script instantiates application instances and forwards requests to them.

entry script for a console application is usually stored in a project base path and named as yii.php. entry script for a web application must be stored under a web accessible directory. it is often called index.php.

the entry scripts do the following −

define constants.
register composer autoloader.
include yii files.
load configuration.
create and configure an application instance.
process the incoming request.

the following is the entry script for the basic application template −

<?php
   //defining global constants
   defined('yii_debug') or define('yii_debug', true);
   defined('yii_env') or define('yii_env', 'dev');
 
   //register composer autoloader
   require(__dir__ . '/../vendor/autoload.php');
   //include yii files
   require(__dir__ . '/../vendor/yiisoft/yii2/yii.php');
  
   //load application config
   $config = require(__dir__ . '/../config/web.php');
  
   //create, config, and process reques
   (new yii\web\application($config))->run();
?>

the following is the entry script for the console application −

#!/usr/bin/env php
<?php
   /** 
   * yii console bootstrap file. 
   * @link http://www.yiiframework.com/ 
   * @copyright copyright (c) 2008 yii software llc 
   * @license http://www.yiiframework.com/license/ 
   */
   //defining global constants
   defined('yii_debug') or define('yii_debug', true);
  
   //register composer autoloader
   require(__dir__ . '/vendor/autoload.php');
   require(__dir__ . '/vendor/yiisoft/yii2/yii.php');
  
   //load config
   $config = require(__dir__ . '/config/console.php');
  
   //apply config the application instance 
   $application = new yii\console\application($config);  

   //process request
   $exitcode = $application->run();
   exit($exitcode);
?>

the best place for defining global constants is entry scripts. there are three supported by yii constants −

yii_debug − defines whether you are in debug mode or not. if set to true, then we will see more log data and detail error call stack.
yii_env − defines the environment mode. the default value is prod. available values are prod, dev, and test. they are used in configuration files to define, for example, a different db connection (local and remote) or other values.
yii_enable_error_handler − specifies whether to enable the default yii error handler.

to define a global constant the following code is used −

//defining global constants 
defined('yii_debug') or define('yii_debug', true); 
which is equivalent to: 
if(!defined('yii_debug')) { 
   define('yii_debug', true); 
}

note − the global constants should be defined at the beginning of an entry script in order to take effect when other php files are included.

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