CI框架源码阅读---------系统初始化文件

文件位置：Location: ./system/core/CodeIgniter.php
CodeIgniter.php 执行流程分析
这是系统初始化文件
1.定义CI版本
2.定义CI分支  这里我认为CI有两个分支一个是Core ，另一个是Reactor。但是这里具体的作用我还没弄白。
3.加载全局函数system/core/common.php
4.加载框架常量  如果定义了ENVIRONMENT常量并且在APPPATH/cofig/下面有以ENVIRONMENT常量为名字的文件夹并且里面存在constants.php则加载这个constants.php
如果没有则直接加载APPPATH/cofig/下面的constants.php
5.定义一个自定义的错误处理函数，让我们用来记录php错误日志
6.如果当前php版本>5.3  则关闭魔术转义
7.设置类前缀（在index.php中可以通过$assign_to_config[]来自定义配置项）
一般的类前缀会在config文件中被设置，这个类前缀可以让CI知道application下的libraries文件夹下哪些的类继承了CI核心类的类，因为CI容许入口文件index.php中覆盖配置文件的配置项，所以程序开始执行之前我们需要知道类前缀是否被覆盖，如果被覆盖了，我们将在所有类加载之前设置它的值。

8.设置脚本执行时间
9.脚本开始执行
加载并实例化基准测试类（类文件：core/Benchmark.php）
记下total_execution_time_start 、loading_time:_base_classes_start这两个时间点
10、如果可以加载并实例化钩子类 （类文件core/Hooks.php）我们就加载并实例化
这需要在钩子是在 application/config/config.php 中开启并在 application/config/hooks.php文件中定义当前的钩子
详情：http://codeigniter.org.cn/user_guide/general/hooks.html
11.加载并实例化配置类
如果我们在index.php中手动的通过$assign_to_config[]来进行配置
12、加载并实例化UTF-8类，这里的顺序是非常重要的UTF-8类必须跟在配置类的后面加载
13、加载并实例化URI类
14、加载并实例化router类，设置router
15、加载并实例化输出类
16、判断有没有缓存文件如果有输出
17、为了防止xss和csrf攻击加载并实例化security类
18、加载并实例化输入类
19、加载并实例化语言包
20、加载并实例化控制器类
get_instance() 这个函数用于实例化控制器类
21、判断是否存在子控制器类 如果存在加载
22、通过控制器去加载本地应用程序下请求的控制器
23、记录loading_time:_base_classes_end时间点
24、进行安全监测 此处有说明：所有的功能不管是应用程序控制器还是加载类可以通过URI调用,控制器function不能用下划线开始
先通过控制器获得加载的类和方法
当加载的类或者方法又或者方法不在CI_Controller这个类中的时候，显示404页面
25、如果设置了pre_controller这个钩子则调用
26、记录请求控制器的时间并且实例化请求的类
27、如果设置了post_controller_constructor这个钩子则调用
28、调用请求的方法
首先监测请求的类中是否有_remap方法，如果有调用
如果没有再判断请求的类中是否有请求的方法如果没有显示404页面
最后调用请求的方法
29、记录控制器执行结束的时间
30、如果设置了post_controller这个钩子则调用
31、将最终的输出发送到浏览器
32、如果设置了post_system钩子则调用

33、判断CI_DB类是否存在还有$CI->db是否设置了值如果为真则关闭数据库连接。

下面是文件源码：

<?php  if ( ! defined('BASEPATH')) exit('No direct script access allowed');
/**
 * CodeIgniter
 *
 * An open source application development framework for PHP 5.1.6 or newer
 *
 * @package		CodeIgniter
 * @author		ExpressionEngine Dev Team
 * @copyright	Copyright (c) 2008 - 2011, EllisLab, Inc.
 * @license		http://codeigniter.com/user_guide/license.html
 * @link		http://codeigniter.com
 * @since		Version 1.0
 * @filesource
 */

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

/**
 * System Initialization File
 *
 * Loads the base classes and executes 执行 the request.
 *
 * @package		CodeIgniter
 * @subpackage	codeigniter
 * @category	Front-controller
 * @author		ExpressionEngine Dev Team
 * @link		http://codeigniter.com/user_guide/
 */

/**
 * CodeIgniter Version
 *
 * @var string
 *
 */
	define('CI_VERSION', '2.1.3');

/**
 * CodeIgniter Branch 分支 (Core = TRUE, Reactor 反应器 = FALSE)
 *
 * @var boolean
 *
 */
	define('CI_CORE', FALSE);

/*
 * ------------------------------------------------------
 *  Load the global functions
 * ------------------------------------------------------
 */
	require(BASEPATH.'core/Common.php');
/*
 * ------------------------------------------------------
 *  Load the framework constants
 * ------------------------------------------------------
 */
	if (defined('ENVIRONMENT') AND file_exists(APPPATH.'config/'.ENVIRONMENT.'/constants.php'))
	{
		require(APPPATH.'config/'.ENVIRONMENT.'/constants.php');
	}
	else
	{
		require(APPPATH.'config/constants.php');
	}

/*
 * ------------------------------------------------------
 *  Define a custom 自定义 error handler 处理器 so we can log PHP errors
 * ------------------------------------------------------
 */
	set_error_handler('_exception_handler');

	if ( ! is_php('5.3'))
	{
		@set_magic_quotes_runtime(0); // Kill magic quotes 关闭魔术转义
	}

/*
 * ------------------------------------------------------
 *  Set the subclass_prefix 类前缀
 * ------------------------------------------------------
 *
 * Normally the "subclass_prefix" is set in the config file.
 * The subclass prefix allows CI to know if a core class is
 * being extended via 通过 a library in the local application
 * "libraries" folder. Since 因为 CI allows config items to be
 * overriden via data set in the main index. php file,
 * before proceeding 开始 、程序 we need to know if a subclass_prefix
 * override exists. 存在  If so, we will set this value now,
 * before any 任何 classes are loaded
 * Note: Since the config file data is cached it doesn't
 * hurt 伤害，使受伤 to load it here.
 * 注意：因为配置文件的数据已经被缓存，所以它加载到这里也不会有伤害。
 */
	if (isset($assign_to_config['subclass_prefix']) AND $assign_to_config['subclass_prefix'] != '')
	{
		get_config(array('subclass_prefix' => $assign_to_config['subclass_prefix']));
	}

/*
 * ------------------------------------------------------
 *  Set a liberal 自由主义者 script execution 执行 time limit
 * ------------------------------------------------------
 */
	if (function_exists("set_time_limit") == TRUE AND @ini_get("safe_mode") == 0)
	{
		@set_time_limit(300);
	}

/*
 * ------------------------------------------------------
 *  Start the timer... tick tock tick tock...
 * ------------------------------------------------------
 */
	$BM =& load_class('Benchmark', 'core');
	$BM->mark('total_execution_time_start');
	$BM->mark('loading_time:_base_classes_start');

/*
 * ------------------------------------------------------
 *  Instantiate the hooks class
 * ------------------------------------------------------
 */
	$EXT =& load_class('Hooks', 'core');

/*
 * ------------------------------------------------------
 *  Is there a "pre_system" hook?
 * ------------------------------------------------------
 */
	$EXT->_call_hook('pre_system');

/*
 * ------------------------------------------------------
 *  Instantiate the config class
 * ------------------------------------------------------
 */
	$CFG =& load_class('Config', 'core');

	// Do we have any manually 手动的 set config items in the index.php file?
	if (isset($assign_to_config))
	{
		$CFG->_assign_to_config($assign_to_config);
	}

/*
 * ------------------------------------------------------
 *  Instantiate the UTF-8 class
 * ------------------------------------------------------
 *
 * Note: Order 命令顺序 here is rather 宁可，当然 important as the UTF-8
 * class needs to be used very early 早期的，提早 on, but it cannot
 * properly 适当的、正确的 determine 决定 if UTf-8 can be supported until 在。。。以前
 * after the Config class is instantiated.
 *
 */

	$UNI =& load_class('Utf8', 'core');

/*
 * ------------------------------------------------------
 *  Instantiate the URI class
 * ------------------------------------------------------
 */
	$URI =& load_class('URI', 'core');

/*
 * ------------------------------------------------------
 *  Instantiate the routing class and set the routing
 * ------------------------------------------------------
 */
	$RTR =& load_class('Router', 'core');
	$RTR->_set_routing();

	// Set any routing overrides that may exist in the main index file
	if (isset($routing))
	{
		$RTR->_set_overrides($routing);
	}

/*
 * ------------------------------------------------------
 *  Instantiate the output class
 * ------------------------------------------------------
 */
	$OUT =& load_class('Output', 'core');

/*
 * ------------------------------------------------------
 *	Is there a valid 有效的 cache file?  If so, we're done...
 * ------------------------------------------------------
 */
	if ($EXT->_call_hook('cache_override') === FALSE)
	{
		if ($OUT->_display_cache($CFG, $URI) == TRUE)
		{
			exit;
		}
	}

/*
 * -----------------------------------------------------
 * Load the security 安全 class for xss and csrf support
 * -----------------------------------------------------
 */
	$SEC =& load_class('Security', 'core');

/*
 * ------------------------------------------------------
 *  Load the Input class and sanitize 使。。。无害 globals
 * ------------------------------------------------------
 */
	$IN	=& load_class('Input', 'core');

/*
 * ------------------------------------------------------
 *  Load the Language class
 * ------------------------------------------------------
 */
	$LANG =& load_class('Lang', 'core');

/*
 * ------------------------------------------------------
 *  Load the app controller and local controller
 * ------------------------------------------------------
 *
 */
	// Load the base controller class
	require BASEPATH.'core/Controller.php';

	function &get_instance()
	{
		return CI_Controller::get_instance();
	}


	if (file_exists(APPPATH.'core/'.$CFG->config['subclass_prefix'].'Controller.php'))
	{
		require APPPATH.'core/'.$CFG->config['subclass_prefix'].'Controller.php';
	}

	// Load the local application controller
	// Note: The Router class automatically 不经思索的、自动的 validates 确认 the controller 
	// path using the router->_validate_request().
	// If this include fails it means 手段、意思是 that 因为、那么 the default controller in 
	// the Routes.php fi.le is not resolving 解析 to something 非常 valid 有效地
	if ( ! file_exists(APPPATH.'controllers/'.$RTR->fetch_directory().$RTR->fetch_class().'.php'))
	{
		show_error('Unable to load your default controller. Please make sure the controller specified in your Routes.php file is valid.');
	}

	include(APPPATH.'controllers/'.$RTR->fetch_directory().$RTR->fetch_class().'.php');

	// Set a mark point for benchmarking 管理标记
	$BM->mark('loading_time:_base_classes_end');

/*
 * ------------------------------------------------------
 *  Security check
 * ------------------------------------------------------
 *
 *  None of the functions in the app controller or the
 *  loader class can be called via the URI, nor 也不是、也没有 can
 *  controller functions that begin with an underscore 下划线、强调、底线
 *  所有的功能不管是应用程序控制器还是加载类可以通过URI调用,控制器function不能用下划线开始
 */
	$class  = $RTR->fetch_class();
	$method = $RTR->fetch_method();

	if ( ! class_exists($class)
		OR strncmp($method, '_', 1) == 0
		OR in_array(strtolower($method), array_map('strtolower', get_class_methods('CI_Controller')))
		)
	{
		if ( ! empty($RTR->routes['404_override']))
		{
			$x = explode('/', $RTR->routes['404_override']);
			$class = $x[0];
			$method = (isset($x[1]) ? $x[1] : 'index');
			if ( ! class_exists($class))
			{
				if ( ! file_exists(APPPATH.'controllers/'.$class.'.php'))
				{
					show_404("{$class}/{$method}");
				}

				include_once(APPPATH.'controllers/'.$class.'.php');
			}
		}
		else
		{
			show_404("{$class}/{$method}");
		}
	}

/*
 * ------------------------------------------------------
 *  Is there a "pre_controller" hook?
 * ------------------------------------------------------
 */
	$EXT->_call_hook('pre_controller');

/*
 * ------------------------------------------------------
 *  Instantiate the requested controller
 * ------------------------------------------------------
 */
	// Mark a start point so we can benchmark the controller
	$BM->mark('controller_execution_time_( '.$class.' / '.$method.' )_start');

	$CI = new $class();

/*
 * ------------------------------------------------------
 *  Is there a "post_controller_constructor" hook?
 * ------------------------------------------------------
 */
	$EXT->_call_hook('post_controller_constructor');

/*
 * ------------------------------------------------------
 *  Call the requested method
 * ------------------------------------------------------
 */
	// Is there a "remap" 重测图、再交换 function? If so, we call it instead 更换、代替
	if (method_exists($CI, '_remap'))
	{
		$CI->_remap($method, array_slice($URI->rsegments, 2));
	}
	else
	{
		// is_callable() returns TRUE on some versions of PHP 5 for private and protected
		// methods, so we'll use this workaround 变通方案 for consistent behavior 一致的行为
		if ( ! in_array(strtolower($method), array_map('strtolower', get_class_methods($CI))))
		{
			// Check and see if we are using a 404 override and use it.
			if ( ! empty($RTR->routes['404_override']))
			{
				$x = explode('/', $RTR->routes['404_override']);
				$class = $x[0];
				$method = (isset($x[1]) ? $x[1] : 'index');
				if ( ! class_exists($class))
				{
					if ( ! file_exists(APPPATH.'controllers/'.$class.'.php'))
					{
						show_404("{$class}/{$method}");
					}

					include_once(APPPATH.'controllers/'.$class.'.php');
					unset($CI);
					$CI = new $class();
				}
			}
			else
			{
				show_404("{$class}/{$method}");
			}
		}

		// Call the requested method.
		// Any URI segments 片段 present 礼物、现在、目前 (besides 除了。。。之外 the class/function) 
		// will be passed to the method for convenience 便利、方便
		call_user_func_array(array(&$CI, $method), array_slice($URI->rsegments, 2));
	}


	// Mark a benchmark end point
	$BM->mark('controller_execution_time_( '.$class.' / '.$method.' )_end');

/*
 * ------------------------------------------------------
 *  Is there a "post_controller" hook?
 * ------------------------------------------------------
 */
	$EXT->_call_hook('post_controller');

/*
 * ------------------------------------------------------
 *  Send the final rendered 提出、已渲染的 output to the browser
 * ------------------------------------------------------
 */
	if ($EXT->_call_hook('display_override') === FALSE)
	{
		$OUT->_display();
	}

/*
 * ------------------------------------------------------
 *  Is there a "post_system" hook?
 * ------------------------------------------------------
 */
	$EXT->_call_hook('post_system');

/*
 * ------------------------------------------------------
 *  Close the DB connection if one exists
 * ------------------------------------------------------
 */
	if (class_exists('CI_DB') AND isset($CI->db))
	{
		$CI->db->close();
	}


/* End of file CodeIgniter.php */
/* Location: ./system/core/CodeIgniter.php */