1.概述
官方注释：
/**
* System Initialization File
*
* Loads the base classes and executes the request.
*
* @package CodeIgniter
* @subpackage CodeIgniter
* @category Front-controller
* @author EllisLab Dev Team
* @link https://codeigniter.com/user_guide/
*/
2.阅读源码
BASEPATH常量是在index.php中定义的，这里判断BASEPATH是否存在是防止用户绕过入口直接返回文件
defined('BASEPATH') OR exit('No direct script access allowed');
版本号
const CI_VERSION = '3.1.10';
加载框架预定义常量
/*
* ------------------------------------------------------
* Load the framework constants
* ------------------------------------------------------
*/
if (file_exists(APPPATH.'config/'.ENVIRONMENT.'/constants.php'))
{
require_once(APPPATH.'config/'.ENVIRONMENT.'/constants.php');
}
if (file_exists(APPPATH.'config/constants.php'))
{
require_once(APPPATH.'config/constants.php');
}
加载全局公共函数
/*
* ------------------------------------------------------
* Load the global functions
* ------------------------------------------------------
*/
require_once(BASEPATH.'core/Common.php');
安全程序
/*
* ------------------------------------------------------
* Security procedures
* ------------------------------------------------------
*/
if ( ! is_php('5.4'))
{
ini_set('magic_quotes_runtime', 0);
if ((bool) ini_get('register_globals'))
{
$_protected = array(
'_SERVER',
'_GET',
'_POST',
'_FILES',
'_REQUEST',
'_SESSION',
'_ENV',
'_COOKIE',
'GLOBALS',
'HTTP_RAW_POST_DATA',
'system_path',
'application_folder',
'view_folder',
'_protected',
'_registered'
);
$_registered = ini_get('variables_order');
foreach (array('E' => '_ENV', 'G' => '_GET', 'P' => '_POST', 'C' => '_COOKIE', 'S' => '_SERVER') as $key => $superglobal)
{
if (strpos($_registered, $key) === FALSE)
{
continue;
}
foreach (array_keys($$superglobal) as $var)
{
if (isset($GLOBALS[$var]) && ! in_array($var, $_protected, TRUE))
{
$GLOBALS[$var] = NULL;
}
}
}
}
}
定义错误处理器
/*
* ------------------------------------------------------
* Define a custom error handler so we can log PHP errors
* ------------------------------------------------------
*/
set_error_handler('_error_handler');
set_exception_handler('_exception_handler');
register_shutdown_function('_shutdown_handler');
$assign_to_config在index.php文件中定义的变量,如果这个变量不为空，则把数组内容赋值到配置参数中去，从这里也可以看得出，assign_to_config的配置优先级是高于配置文件的
if ( ! empty($assign_to_config['subclass_prefix']))
{
get_config(array('subclass_prefix' => $assign_to_config['subclass_prefix']));
}
是否使用Composer
/*
* ------------------------------------------------------
* Should we use a Composer autoloader?
* ------------------------------------------------------
*/
if ($composer_autoload = config_item('composer_autoload'))
{
if ($composer_autoload === TRUE)
{
file_exists(APPPATH.'vendor/autoload.php')
? require_once(APPPATH.'vendor/autoload.php')
: log_message('error', '$config[\'composer_autoload\'] is set to TRUE but '.APPPATH.'vendor/autoload.php was not found.');
}
elseif (file_exists($composer_autoload))
{
require_once($composer_autoload);
}
else
{
log_message('error', 'Could not find the specified $config[\'composer_autoload\'] path: '.$composer_autoload);
}
}
加载Benchmark组件，监测跟踪性能
/*
* ------------------------------------------------------
* 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');
加载Hooks组件，Hooks组件可以在不改变系统代码的情况下增加扩展功能，扩展方式就是在系统某个位置放置挂钩点，例如：pre_system，就是放置在系统中的挂钩点
/*
* ------------------------------------------------------
* Instantiate the hooks class
* ------------------------------------------------------
*/
$EXT =& load_class('Hooks', 'core');
/*
* ------------------------------------------------------
* Is there a "pre_system" hook?
* ------------------------------------------------------
*/
$EXT->call_hook('pre_system');
加载Config组件， Config组件是对配置参数进行管理，如果assign_to_config变量不为空，则将其值添加到配置参数中
/*
* ------------------------------------------------------
* Instantiate the config class
* ------------------------------------------------------
*
* Note: It is important that Config is loaded first as
* most other classes depend on it either directly or by
* depending on another class that uses it.
*
*/
$CFG =& load_class('Config', 'core');
// Do we have any manually set config items in the index.php file?
if (isset($assign_to_config) && is_array($assign_to_config))
{
foreach ($assign_to_config as $key => $value)
{
$CFG->set_item($key, $value);
}
}
设置字符串编码格式
/*
* ------------------------------------------------------
* Important charset-related stuff
* ------------------------------------------------------
*
* Configure mbstring and/or iconv if they are enabled
* and set MB_ENABLED and ICONV_ENABLED constants, so
* that we don't repeatedly do extension_loaded() or
* function_exists() calls.
*
* Note: UTF-8 class depends on this. It used to be done
* in it's constructor, but it's _not_ class-specific.
*
*/
$charset = strtoupper(config_item('charset'));
ini_set('default_charset', $charset);
if (extension_loaded('mbstring'))
{
define('MB_ENABLED', TRUE);
// mbstring.internal_encoding is deprecated starting with PHP 5.6
// and it's usage triggers E_DEPRECATED messages.
@ini_set('mbstring.internal_encoding', $charset);
// This is required for mb_convert_encoding() to strip invalid characters.
// That's utilized by CI_Utf8, but it's also done for consistency with iconv.
mb_substitute_character('none');
}
else
{
define('MB_ENABLED', FALSE);
}
// There's an ICONV_IMPL constant, but the PHP manual says that using
// iconv's predefined constants is "strongly discouraged".
if (extension_loaded('iconv'))
{
define('ICONV_ENABLED', TRUE);
// iconv.internal_encoding is deprecated starting with PHP 5.6
// and it's usage triggers E_DEPRECATED messages.
@ini_set('iconv.internal_encoding', $charset);
}
else
{
define('ICONV_ENABLED', FALSE);
}
if (is_php('5.6'))
{
ini_set('php.internal_encoding', $charset);
}
加载兼容性功能
/*
* ------------------------------------------------------
* Load compatibility features
* ------------------------------------------------------
*/
require_once(BASEPATH.'core/compat/mbstring.php');
require_once(BASEPATH.'core/compat/hash.php');
require_once(BASEPATH.'core/compat/password.php');
require_once(BASEPATH.'core/compat/standard.php');
加载UTF-8组件
/*
* ------------------------------------------------------
* Instantiate the UTF-8 class
* ------------------------------------------------------
*/
$UNI =& load_class('Utf8', 'core');
加载URI组件
/*
* ------------------------------------------------------
* Instantiate the URI class
* ------------------------------------------------------
*/
$URI =& load_class('URI', 'core');
加载Router组件
/*
* ------------------------------------------------------
* Instantiate the routing class and set the routing
* ------------------------------------------------------
*/
$RTR =& load_class('Router', 'core', isset($routing) ? $routing : NULL);
加载Output组件
/*
* ------------------------------------------------------
* Instantiate the output class
* ------------------------------------------------------
*/
$OUT =& load_class('Output', 'core');
cache_override是一个挂钩点，这个挂钩点可以自定义缓存策略，如果没有扩展这个钩子，查看输出组件是否有缓存，有缓存则直接输出
/*
* ------------------------------------------------------
* Is there a valid cache file? If so, we're done...
* ------------------------------------------------------
*/
if ($EXT->call_hook('cache_override') === FALSE && $OUT->_display_cache($CFG, $URI) === TRUE)
{
exit;
}
缓存没有命中才会继续执行
加载Security组件，可以防范xss，csrf等网络攻击
/*
* -----------------------------------------------------
* Load the security class for xss and csrf support
* -----------------------------------------------------
*/
$SEC =& load_class('Security', 'core');
加载Input组件，可通过input读取客户端输入，表单提交等数据
/*
* ------------------------------------------------------
* Load the Input class and sanitize globals
* ------------------------------------------------------
*/
$IN =& load_class('Input', 'core');
加载Lang组件
/*
* ------------------------------------------------------
* Load the Language class
* ------------------------------------------------------
*/
$LANG =& load_class('Lang', 'core');
加载控制器基类
/*
* ------------------------------------------------------
* Load the app controller and local controller
* ------------------------------------------------------
*
*/
// Load the base controller class
require_once BASEPATH.'core/Controller.php';
/**
* Reference to the CI_Controller method.
*
* Returns current CI instance object
*
* @return CI_Controller
*/
function &get_instance()
{
return CI_Controller::get_instance();
}
if (file_exists(APPPATH.'core/'.$CFG->config['subclass_prefix'].'Controller.php'))
{
require_once APPPATH.'core/'.$CFG->config['subclass_prefix'].'Controller.php';
}
理智检查，检查类和方法
/*
* ------------------------------------------------------
* Sanity checks
* ------------------------------------------------------
*
* The Router class has already validated the request,
* leaving us with 3 options here:
*
* 1) an empty class name, if we reached the default
* controller, but it didn't exist;
* 2) a query string which doesn't go through a
* file_exists() check
* 3) a regular request for a non-existing page
*
* We handle all of these as a 404 error.
*
* Furthermore, none of the methods in the app controller
* or the loader class can be called via the URI, nor can
* controller methods that begin with an underscore.
*/
$e404 = FALSE;
$class = ucfirst($RTR->class);
$method = $RTR->method;
if (empty($class) OR ! file_exists(APPPATH.'controllers/'.$RTR->directory.$class.'.php'))
{
$e404 = TRUE;
}
else
{
require_once(APPPATH.'controllers/'.$RTR->directory.$class.'.php');
if ( ! class_exists($class, FALSE) OR $method[0] === '_' OR method_exists('CI_Controller', $method))
{
$e404 = TRUE;
}
elseif (method_exists($class, '_remap'))
{
$params = array($method, array_slice($URI->rsegments, 2));
$method = '_remap';
}
elseif ( ! method_exists($class, $method))
{
$e404 = TRUE;
}
/**
* DO NOT CHANGE THIS, NOTHING ELSE WORKS!
*
* - method_exists() returns true for non-public methods, which passes the previous elseif
* - is_callable() returns false for PHP 4-style constructors, even if there's a __construct()
* - method_exists($class, '__construct') won't work because CI_Controller::__construct() is inherited
* - People will only complain if this doesn't work, even though it is documented that it shouldn't.
*
* ReflectionMethod::isConstructor() is the ONLY reliable check,
* knowing which method will be executed as a constructor.
*/
elseif ( ! is_callable(array($class, $method)))
{
$reflection = new ReflectionMethod($class, $method);
if ( ! $reflection->isPublic() OR $reflection->isConstructor())
{
$e404 = TRUE;
}
}
}
if ($e404)
{
if ( ! empty($RTR->routes['404_override']))
{
if (sscanf($RTR->routes['404_override'], '%[^/]/%s', $error_class, $error_method) !== 2)
{
$error_method = 'index';
}
$error_class = ucfirst($error_class);
if ( ! class_exists($error_class, FALSE))
{
if (file_exists(APPPATH.'controllers/'.$RTR->directory.$error_class.'.php'))
{
require_once(APPPATH.'controllers/'.$RTR->directory.$error_class.'.php');
$e404 = ! class_exists($error_class, FALSE);
}
// Were we in a directory? If so, check for a global override
elseif ( ! empty($RTR->directory) && file_exists(APPPATH.'controllers/'.$error_class.'.php'))
{
require_once(APPPATH.'controllers/'.$error_class.'.php');
if (($e404 = ! class_exists($error_class, FALSE)) === FALSE)
{
$RTR->directory = '';
}
}
}
else
{
$e404 = FALSE;
}
}
// Did we reset the $e404 flag? If so, set the rsegments, starting from index 1
if ( ! $e404)
{
$class = $error_class;
$method = $error_method;
$URI->rsegments = array(
1 => $class,
2 => $method
);
}
else
{
show_404($RTR->directory.$class.'/'.$method);
}
}
if ($method !== '_remap')
{
$params = array_slice($URI->rsegments, 2);
}
运行控制器方法
/*
* ------------------------------------------------------
* 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?
* ------------------------------------------------------
*/
$EXT->call_hook('post_controller_constructor');
/*
* ------------------------------------------------------
* Call the requested method
* ------------------------------------------------------
*/
call_user_func_array(array(&$CI, $method), $params);
// Mark a benchmark end point
$BM->mark('controller_execution_time_( '.$class.' / '.$method.' )_end');
/*
* ------------------------------------------------------
* Is there a "post_controller" hook?
* ------------------------------------------------------
*/
$EXT->call_hook('post_controller');
输出内容
/*
* ------------------------------------------------------
* Send the final rendered output to the browser
* ------------------------------------------------------
*/
if ($EXT->call_hook('display_override') === FALSE)
{
$OUT->_display();
}
/*
* ------------------------------------------------------
* Is there a "post_system" hook?
* ------------------------------------------------------
*/
$EXT->call_hook('post_system');
此处回顾整个代码流程：
