CodeIgniter框架源码学习之配置类－－Config.php

文件位置：./system/core/Config.php
1.成员属性$config 所有已加载配置的值的列表
2.成员属性$is_loaded 所有加载配置文件的列表
3.成员属性$_config_paths 当需要加载配置文件的时候搜索路径的列表
4.__construct() 构造方法程序会首先自动执行这个方法
它所做的内容主要有两个  a)获取配置赋值给成员属性$config
b)设置配置中的base_url
5.load($file = '', $use_sections = FALSE, $fail_gracefully = FALSE)
加载配置文件
$file 是你自定义的配置文件的文件名，这个文件名没有 .php 的扩展名. 
$use_sections  如果你需要加载多个自定义配置文件，一般情况下它们会被合并成一个数组。然而，如果在不同的配置文件中存在同名的索引，那么会发生冲突。为了避免这个问题，你可以把第二个参数设置为 TRUE ，这可以使每个配置文件的内容存储在一个单独的数组中，数组的索引就是配置文件的文件名。
$fail_gracefully允许屏蔽当配置文件不存在时产生的错误信息:
(0)过滤并设置$file 变量
(1)初始化$founf 为FALSE 用于判断文件是否存在
(2)初始化$loaded为FALSE 用于判断文件是否被加载
(3)检测文件路径如果有环境变量添加环境变量
(4)进入foreach遍历文件路径，并查找文件是否被加载和存在
(5)如果文件不存在跳出foreach循环
(6)加载文件
(7)判断$config是否存在，这个$config 应该是加载的文件中定义的
(8)判断$use_sections 如果为真则将使每个配置文件的内容存储在一个单独的数组中，数组的索引就是配置文件的文件名。
  如果为假则所有配置文件会被合并成一个数组
(9)将文件添加进is_loaded数组中，并销毁$config
(10)$loaded 设置为true log记录 跳出循环
(11)如果loaded为false并且$fail_gracefully不等于true 显示错误日志

6.item() 获取一个配置项
$item 配置项的名字
$index  如果配置是一个数组的时候，这一项是数组索引名字
(1)判断index是否为空
(2)如果index为空，判断$this->config[$item]是否存在，如果不存在返回，存在，赋值给$pref
(3)如果index不为空，判断$this->config[$index]是否存在，判断$this->config[$index][$item]是否存在，将$this->config[$index][$item]赋值给$pref
(4)返回$pref

7.slash_item() 获取一个配置项并添加/
$item 配置项的名字
(1)判断配置项是否存在不存在返回false
(2)判断配置项是否为空如果是空返回''
(3)在配置值的后面添加/并返回。

8.site_url() 该函数得到你网站的 URL，其中包含了你在 config 文件中设置的 "index" 的值。
$uri uri字符串就是访问路径所带的参数
(1) 如果$uri = '' 返回由base_url和index_page组成的url
(2) 判断$this->item('enable_query_strings')真假，并返回不同形式的地址。(这一项是在application/config/config.php文件中配置的。用来区分传参方式，如果为false就是默认的传参方式example.com/who/what/where/。如果为true就是
example.com/index.php?c=controller&m=function这样的传参方式。)

9.base_url() 该函数返回站点的根 URL，可以在这个函数后拼接一个 URL 路径，用以生成 CSS 或图片文件的 URL。

10._uri_string() 构建uri串让site_url()，base_url()两个函数使用。

11.system_url() 该函数得到 system 文件夹的 URL。

12.set_item()  设置一个配置项

贴上代码：

<?php
/**
* CodeIgniter
*
* An open source application development framework for PHP
*
* This content is released under the MIT License (MIT)
*
* Copyright (c) 2014 - 2017, British Columbia Institute of Technology
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*
* @package	CodeIgniter
* @author	EllisLab Dev Team
* @copyright	Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)
* @copyright	Copyright (c) 2014 - 2017, British Columbia Institute of Technology (http://bcit.ca/)
* @license http://opensource.org/licenses/MIT MIT License
* @link https://codeigniter.com * @since	Version 1.0.0
* @filesource
*/
defined('BASEPATH') OR exit('No direct script access allowed');

/**
* Config Class
*
* This class contains functions that enable config files to be managed
*
* @package		CodeIgniter
* @subpackage	Libraries
* @category	Libraries
* @author		EllisLab Dev Team
* @link	 https://codeigniter.com/user_guide/libraries/config.html */
class CI_Config {

/**
* List of all loaded config values
*
* @var	array
*/
public $config = array();

/**
* List of all loaded config files
*
* @var	array
*/
public $is_loaded =	array();

/**
* List of paths to search when trying to load a config file.
*
* @used-by	CI_Loader
* @var		array
*/
public $_config_paths =	array(APPPATH);

// --------------------------------------------------------------------

/**
* Class constructor
*
* Sets the $config data from the primary config.php file as a class variable.
*
* @return	void
*/
public function __construct()
{
$this->config =& get_config();

// Set the base_url automatically if none was provided
if (empty($this->config['base_url']))
{
if (isset($_SERVER['SERVER_ADDR']))
{
if (strpos($_SERVER['SERVER_ADDR'], ':') !== FALSE)
{
$server_addr = '['.$_SERVER['SERVER_ADDR'].']';
}
else
{
$server_addr = $_SERVER['SERVER_ADDR'];
}

$base_url = (is_https() ? 'https' : 'http').'://'.$server_addr
.substr($_SERVER['SCRIPT_NAME'], 0, strpos($_SERVER['SCRIPT_NAME'], basename($_SERVER['SCRIPT_FILENAME'])));
}
else
{
$base_url = 'http://localhost/';
}

$this->set_item('base_url', $base_url);
}

log_message('info', 'Config Class Initialized');
}

// --------------------------------------------------------------------

/**
* Load Config File
*
* @param	string	$file			Configuration file name
* @param	bool	$use_sections		Whether configuration values should be loaded into their own section
* @param	bool	$fail_gracefully	Whether to just return FALSE or display an error message
* @return	bool	TRUE if the file was loaded correctly or FALSE on failure
*/
public function load($file = '', $use_sections = FALSE, $fail_gracefully = FALSE)
{
$file = ($file === '') ? 'config' : str_replace('.php', '', $file);
$loaded = FALSE;

foreach ($this->_config_paths as $path)
{
foreach (array($file, ENVIRONMENT.DIRECTORY_SEPARATOR.$file) as $location)
{
$file_path = $path.'config/'.$location.'.php';
if (in_array($file_path, $this->is_loaded, TRUE))
{
return TRUE;
}

if ( ! file_exists($file_path))
{
continue;
}

include($file_path);

if ( ! isset($config) OR ! is_array($config))
{
if ($fail_gracefully === TRUE)
{
return FALSE;
}

show_error('Your '.$file_path.' file does not appear to contain a valid configuration array.');
}

if ($use_sections === TRUE)
{
$this->config[$file] = isset($this->config[$file])
? array_merge($this->config[$file], $config)
: $config;
}
else
{
$this->config = array_merge($this->config, $config);
}

$this->is_loaded[] = $file_path;
$config = NULL;
$loaded = TRUE;
log_message('debug', 'Config file loaded: '.$file_path);
}
}

if ($loaded === TRUE)
{
return TRUE;
}
elseif ($fail_gracefully === TRUE)
{
return FALSE;
}

show_error('The configuration file '.$file.'.php does not exist.');
}

// --------------------------------------------------------------------

/**
* Fetch a config file item
*
* @param	string	$item	Config item name
* @param	string	$index	Index name
* @return	string|null	The configuration item or NULL if the item doesn't exist
*/
public function item($item, $index = '')
{
if ($index == '')
{
return isset($this->config[$item]) ? $this->config[$item] : NULL;
}

return isset($this->config[$index], $this->config[$index][$item]) ? $this->config[$index][$item] : NULL;
}

// --------------------------------------------------------------------

/**
* Fetch a config file item with slash appended (if not empty)
*
* @param	string		$item	Config item name
* @return	string|null	The configuration item or NULL if the item doesn't exist
*/
public function slash_item($item)
{
if ( ! isset($this->config[$item]))
{
return NULL;
}
elseif (trim($this->config[$item]) === '')
{
return '';
}

return rtrim($this->config[$item], '/').'/';
}

// --------------------------------------------------------------------

/**
* Site URL
*
* Returns base_url . index_page [. uri_string]
*
* @uses	CI_Config::_uri_string()
*
* @param	string|string[]	$uri	URI string or an array of segments
* @param	string	$protocol
* @return	string
*/
public function site_url($uri = '', $protocol = NULL)
{
$base_url = $this->slash_item('base_url');

if (isset($protocol))
{
// For protocol-relative links
if ($protocol === '')
{
$base_url = substr($base_url, strpos($base_url, '//'));
}
else
{
$base_url = $protocol.substr($base_url, strpos($base_url, '://'));
}
}

if (empty($uri))
{
return $base_url.$this->item('index_page');
}

$uri = $this->_uri_string($uri);

if ($this->item('enable_query_strings') === FALSE)
{
$suffix = isset($this->config['url_suffix']) ? $this->config['url_suffix'] : '';

if ($suffix !== '')
{
if (($offset = strpos($uri, '?')) !== FALSE)
{
$uri = substr($uri, 0, $offset).$suffix.substr($uri, $offset);
}
else
{
$uri .= $suffix;
}
}

return $base_url.$this->slash_item('index_page').$uri;
}
elseif (strpos($uri, '?') === FALSE)
{
$uri = '?'.$uri;
}

return $base_url.$this->item('index_page').$uri;
}

// -------------------------------------------------------------

/**
* Base URL
*
* Returns base_url [. uri_string]
*
* @uses	CI_Config::_uri_string()
*
* @param	string|string[]	$uri	URI string or an array of segments
* @param	string	$protocol
* @return	string
*/
public function base_url($uri = '', $protocol = NULL)
{
$base_url = $this->slash_item('base_url');

if (isset($protocol))
{
// For protocol-relative links
if ($protocol === '')
{
$base_url = substr($base_url, strpos($base_url, '//'));
}
else
{
$base_url = $protocol.substr($base_url, strpos($base_url, '://'));
}
}

return $base_url.$this->_uri_string($uri);
}

// -------------------------------------------------------------

/**
* Build URI string
*
* @used-by	CI_Config::site_url()
* @used-by	CI_Config::base_url()
*
* @param	string|string[]	$uri	URI string or an array of segments
* @return	string
*/
protected function _uri_string($uri)
{
if ($this->item('enable_query_strings') === FALSE)
{
is_array($uri) && $uri = implode('/', $uri);
return ltrim($uri, '/');
}
elseif (is_array($uri))
{
return http_build_query($uri);
}

return $uri;
}

// --------------------------------------------------------------------

/**
* System URL
*
* @deprecated	3.0.0	Encourages insecure practices
* @return	string
*/
public function system_url()
{
$x = explode('/', preg_replace('|/*(.+?)/*$|', '\\1', BASEPATH));
return $this->slash_item('base_url').end($x).'/';
}

// --------------------------------------------------------------------

/**
* Set a config file item
*
* @param	string	$item	Config item key
* @param	string	$value	Config item value
* @return	void
*/
public function set_item($item, $value)
{
$this->config[$item] = $value;
}

}