CI框架入口文件index.php文件分析​ 推荐

<?php
/*
*---------------------------------------------------------------
* APPLICATION ENVIRONMENT
*---------------------------------------------------------------
*
* You can load different configurations depending on your
* current environment. Setting the environment also influences
* things like logging and error reporting.
*
* This can be set to anything, but default usage is:
*
*     development
*     testing
*     production
*
* NOTE: If you change these, also change the error_reporting() code below
*
*/
//设置环境配置,development,testing,production三种。其本质就是设置error_reporting()的级别
define('ENVIRONMENT', 'development');
/*
*---------------------------------------------------------------
* ERROR REPORTING
*---------------------------------------------------------------
*
* Different environments will require different levels of error reporting.
* By default development will show errors but testing and live will hide them.
*/
//根据选择的环境，设置error_reporting()的级别
if (defined('ENVIRONMENT'))
{
switch (ENVIRONMENT)
{
case 'development':
error_reporting(E_ALL);
break;

case 'testing':
case 'production':
error_reporting(0);
break;
default:
exit('The application environment is not set correctly.');
}
}
/*
*---------------------------------------------------------------
* SYSTEM FOLDER NAME
*---------------------------------------------------------------
*
* This variable must contain the name of your "system" folder.
* Include the path if the folder is not in the same  directory
* as this file.
*
*/
//设置系统的路径,必须包含system这个目录，这是CI的核心所在目录
$system_path = 'system';
/*
*---------------------------------------------------------------
* APPLICATION FOLDER NAME
*---------------------------------------------------------------
*
* If you want this front controller to use a different "application"
* folder then the default one you can set its name here. The folder
* can also be renamed or relocated anywhere on your server.  If
* you do, use a full server path. For more info please see the user guide:
* http://codeigniter.com/user_guide/general/managing_apps.html *
* NO TRAILING SLASH!
*
*/
//设置个人应用的目录
$application_folder = 'application';
/*
* --------------------------------------------------------------------
* DEFAULT CONTROLLER
* --------------------------------------------------------------------
*
* Normally you will set your default controller in the routes.php file.
* You can, however, force a custom routing by hard-coding a
* specific controller class/function here.  For most applications, you
* WILL NOT set your routing here, but it's an option for those
* special instances where you might want to override the standard
* routing in a specific front controller that shares a common CI installation.
*
* IMPORTANT:  If you set the routing here, NO OTHER controller will be
* callable. In essence, this preference limits your application to ONE
* specific controller.  Leave the function name blank if you need
* to call functions dynamically via the URI.
*
* Un-comment the $routing array below to use this feature
*
*/
//用于设置额外的控制器目录,当你的控制器没有放在application/controllers的时候需要通过以下配置来指定你的controllers目录的位置
//总共有三种方式,第一种指定控制器的目录，第二种指定控制的类名，第三种指定控制器中函数名称
// The directory name, relative to the "controllers" folder.  Leave blank
// if your controller is not in a sub-folder within the "controllers" folder
// $routing['directory'] = '';
// The controller class file name.  Example:  Mycontroller
// $routing['controller'] = '';
// The controller function you wish to be called.
// $routing['function'] = '';
//下面是用来定制一些配置参数
//允许你设置一些参数，或者覆盖任何在config.php文件的中的默认配置值
/*
* -------------------------------------------------------------------
*  CUSTOM CONFIG VALUES
* -------------------------------------------------------------------
*
* The $assign_to_config array below will be passed dynamically to the
* config class when initialized. This allows you to set custom config
* items or override any default config values found in the config.php file.
* This can be handy as it permits you to share one application between
* multiple front controller files, with each file containing different
* config values.
*
* Un-comment the $assign_to_config array below to use this feature
*
*/
// $assign_to_config['name_of_config_item'] = 'value of config item';
//下面是不要编辑的地方
// --------------------------------------------------------------------
// END OF USER CONFIGURABLE SETTINGS.  DO NOT EDIT BELOW THIS LINE
// --------------------------------------------------------------------
/*
* ---------------------------------------------------------------
*  Resolve the system path for increased reliability
* ---------------------------------------------------------------
*/
// Set the current directory correctly for CLI requests
// 对于当前的请求，将请求转至定义的目录
if (defined('STDIN'))
{
//dirname(__FILE__) 返回当前文件的目录,并通过chdir切换过去。
chdir(dirname(__FILE__));
}
//realpath 返回指定文件的绝对路径
//
if (realpath($system_path) !== FALSE)
{
//设置成绝对路径,并在最后添加/ 补全路径
$system_path = realpath($system_path).'/';
}
//确保有一个斜线
// ensure there's a trailing slash
$system_path = rtrim($system_path, '/').'/';
//判断这个路径是否存在
// Is the system path correct?
if ( ! is_dir($system_path))
{
exit("Your system folder path does not appear to be set correctly. Please open the following file and correct this: ".pathinfo(__FILE__, PATHINFO_BASENAME));
//path 获取文件路径信息
//    PATHINFO_DIRNAME - 只返回 dirname
//    PATHINFO_BASENAME - 只返回 basename
//    PATHINFO_EXTENSION - 只返回 extension
}
//现在我们知道了路径的相关信息了,就可以来定义一些信息了
/*
* -------------------------------------------------------------------
*  Now that we know the path, set the main path constants
* -------------------------------------------------------------------
*/
// The name of THIS file
define('SELF', pathinfo(__FILE__, PATHINFO_BASENAME));
// The PHP file extension
// this global constant is deprecated.
define('EXT', '.php');
// Path to the system folder
//将\\替换成 /
define('BASEPATH', str_replace("\\", "/", $system_path));
// Path to the front controller (this file)

define('FCPATH', str_replace(SELF, '', __FILE__));
// Name of the "system folder"
define('SYSDIR', trim(strrchr(trim(BASEPATH, '/'), '/'), '/'));
// The path to the "application" folder
//定义APP的目录，从中可以发现APP目录有两个一个是和system同一级目录，还有一个就是在system的子目录中
if (is_dir($application_folder))
{
define('APPPATH', $application_folder.'/');
}
else
{
if ( ! is_dir(BASEPATH.$application_folder.'/'))
{
exit("Your application folder path does not appear to be set correctly. Please open the following file and correct this: ".SELF);
}
define('APPPATH', BASEPATH.$application_folder.'/');
}
/*
* --------------------------------------------------------------------
* LOAD THE BOOTSTRAP FILE
* --------------------------------------------------------------------
*
* And away we go...
*
*/
//加载启动文件
require_once BASEPATH.'core/CodeIgniter.php';
/* End of file index.php */
/* Location: ./index.php */