CI框架源码阅读---------Config.php

文件地址：./system/core/Config.php
主要作用：管理配置
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


13._assign_to_config() 设置多个配置项(以数组的形式key是要设置的配置项的名字，value 是配置项的值)

源码：

<?php  if ( ! defined('BASEPATH')) exit('No direct script access allowed');/** * CodeIgniter * * An open source application development framework for PHP 5.1.6 or newer * * @packageCodeIgniter * @authorExpressionEngine Dev Team * @copyrightCopyright (c) 2008 - 2011, EllisLab, Inc. * @licensehttp://codeigniter.com/user_guide/license.html * @linkhttp://codeigniter.com * @sinceVersion 1.0 * @filesource */// ------------------------------------------------------------------------/** * CodeIgniter Config Class * * This class contains functions that enable config files to be managed * * @packageCodeIgniter * @subpackageLibraries * @categoryLibraries * @authorExpressionEngine Dev Team * @linkhttp://codeigniter.com/user_guide/libraries/config.html */class CI_Config {/** * List of all loaded config values * * @var array */var $config = array();/** * List of all loaded config files * * @var array */var $is_loaded = array();/** * List of paths to search when trying to load a config file * * @var array */var $_config_paths = array(APPPATH);/** * Constructor * * Sets the $config data from the primary config.php file as a class variable * * @access   public * @param   stringthe config file name * @param   boolean  if configuration values should be loaded into their own section * @param   boolean  true if errors should just return false, false if an error message should be displayed * @return  boolean  if the file was successfully loaded or not */function __construct(){$this->config =& get_config();log_message('debug', "Config Class Initialized");// Set the base_url automatically if none was provided 假如if ($this->config['base_url'] == ''){if (isset($_SERVER['HTTP_HOST'])){$base_url = isset($_SERVER['HTTPS']) && strtolower($_SERVER['HTTPS']) !== 'off' ? 'https' : 'http';$base_url .= '://'. $_SERVER['HTTP_HOST'];$base_url .= str_replace(basename($_SERVER['SCRIPT_NAME']), '', $_SERVER['SCRIPT_NAME']);}else{$base_url = 'http://localhost/';}$this->set_item('base_url', $base_url);}}// --------------------------------------------------------------------/** * Load Config File * * @accesspublic * @paramstringthe config file name * @param   boolean  if configuration values should be loaded into their own section * @param   boolean  true if errors should just return false, false if an error message should be displayed * @returnbooleanif the file was loaded correctly */function load($file = '', $use_sections = FALSE, $fail_gracefully = FALSE){$file = ($file == '') ? 'config' : str_replace('.php', '', $file);$found = FALSE;$loaded = FALSE;$check_locations = defined('ENVIRONMENT')? array(ENVIRONMENT.'/'.$file, $file): array($file);foreach ($this->_config_paths as $path){foreach ($check_locations as $location){$file_path = $path.'config/'.$location.'.php';if (in_array($file_path, $this->is_loaded, TRUE)){$loaded = TRUE;continue 2;}if (file_exists($file_path)){$found = TRUE;break;}}if ($found === FALSE){continue;}include($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 ($use_sections === TRUE){if (isset($this->config[$file])){$this->config[$file] = array_merge($this->config[$file], $config);}else{$this->config[$file] = $config;}}else{$this->config = array_merge($this->config, $config);}$this->is_loaded[] = $file_path;unset($config);$loaded = TRUE;log_message('debug', 'Config file loaded: '.$file_path);break;}if ($loaded === FALSE){if ($fail_gracefully === TRUE){return FALSE;}show_error('The configuration file '.$file.'.php does not exist.');}return TRUE;}// --------------------------------------------------------------------/** * Fetch 取得，拿来 a config file item * * * @accesspublic * @paramstringthe config item name * @paramstringthe index name * @parambool * @returnstring */function item($item, $index = ''){if ($index == ''){if ( ! isset($this->config[$item])){return FALSE;}$pref = $this->config[$item];}else{if ( ! isset($this->config[$index])){return FALSE;}if ( ! isset($this->config[$index][$item])){return FALSE;}$pref = $this->config[$index][$item];}return $pref;}// --------------------------------------------------------------------/** * Fetch a config file item - adds slash after item (if item is not empty) * * @accesspublic * @paramstringthe config item name * @parambool * @returnstring */function slash_item($item){if ( ! isset($this->config[$item])){return FALSE;}if( trim($this->config[$item]) == ''){return '';}return rtrim($this->config[$item], '/').'/';}// --------------------------------------------------------------------/** * Site URL * Returns base_url . index_page [. uri_string] * * @accesspublic * @paramstringthe URI string * @returnstring */function site_url($uri = ''){if ($uri == ''){return $this->slash_item('base_url').$this->item('index_page');}if ($this->item('enable_query_strings') == FALSE){$suffix = ($this->item('url_suffix') == FALSE) ? '' : $this->item('url_suffix');return $this->slash_item('base_url').$this->slash_item('index_page').$this->_uri_string($uri).$suffix;}else{return $this->slash_item('base_url').$this->item('index_page').'?'.$this->_uri_string($uri);}}// -------------------------------------------------------------/** * Base URL * Returns base_url [. uri_string] * * @access public * @param string $uri * @return string */function base_url($uri = ''){return $this->slash_item('base_url').ltrim($this->_uri_string($uri), '/');}// -------------------------------------------------------------/** * Build URI string for use in Config::site_url() and Config::base_url() * * @access protected * @param  $uri * @return string */protected function _uri_string($uri){if ($this->item('enable_query_strings') == FALSE){if (is_array($uri)){$uri = implode('/', $uri);}$uri = trim($uri, '/');}else{if (is_array($uri)){$i = 0;$str = '';foreach ($uri as $key => $val){$prefix = ($i == 0) ? '' : '&';$str .= $prefix.$key.'='.$val;$i++;}$uri = $str;}}    return $uri;}// --------------------------------------------------------------------/** * System URL * * @accesspublic * @returnstring */function system_url(){$x = explode("/", preg_replace("|/*(.+?)/*$|", "\\1", BASEPATH));return $this->slash_item('base_url').end($x).'/';}// --------------------------------------------------------------------/** * Set a config file item * * @accesspublic * @paramstringthe config item key * @paramstringthe config item value * @returnvoid */function set_item($item, $value){$this->config[$item] = $value;}// --------------------------------------------------------------------/** * Assign to Config * * This function is called by the front controller (CodeIgniter.php) * after the Config class is instantiated.  It permits config items * to be assigned or overriden by variables contained in the index.php file * * @accessprivate * @paramarray * @returnvoid */function _assign_to_config($items = array()){if (is_array($items)){foreach ($items as $key => $val){$this->set_item($key, $val);}}}}// END CI_Config class/* End of file Config.php *//* Location: ./system/core/Config.php */