它将把各个类库串联了起来,故事从这里正式开始。

知识点

$GLOBALS 是一个包含了全部变量的全局组合数组,变量的名字就是数组的键。

流程

  1. 引入 Constants.php 定义全局变量。
  2. 引入 Common.php 定义全局函数。
  3. 当 php version 小于 5.4 时,处理 register_globals 带来的安全问题。
  4. 绑定 error handler
    4.1 set_error_handler(‘_error_handler’);
    4.2 set_exception_handler(‘_exception_handler’);
    4.3 register_shutdown_function(‘_shutdown_handler’);
  5. 修改自定义类前缀subclass_prefix(默认MY_)
  6. 定义 comoser 的 autoloader
  7. 引入 Benchmark 类($BM
  8. 引入 Hooks 类 ($EXT
  9. 执行钩子 pre_system
  10. 引入 Config 类($CFG
  11. 设置编码
    11.1 mbstring.internal_encoding
    11.2 iconv.internal_encoding
    11.3 php.internal_encoding
  12. 引入 BASEPATH.’core/compat/*’ 相关函数
    12.1 mbstring.php
    12.2 hash.php
    12.3 password.php
    12.4 standard.php
  13. 引入核心类
    13.1 Utf-8 类 ($UNI
    13.2 Uri 类($URI
    13.3 Router类($RTR)尽兴路由检测
    13.4 Output$OUT
  14. 检测 cache_override 参数,如果不存在则检测是否有 缓存 存在。
  15. 继续引入类
    15.1 Input 类($IN
    15.2 Language 类($LANG
    15.3 Controller 类
    15.3.4 引入重写的 Controller 类
  16. 404 检测
  17. 检测 _remap 函数调用参数
  18. 调用钩子 pre_controller
  19. 创建请求的类 $CI
  20. 执行钩子 post_controller_constructor
  21. 执行请求的方法
  22. 执行钩子 post_controller
  23. 执行钩子 display_override ,如果没有,则正常显示
  24. 执行钩子 post_system

源码分析


<?php
/**
 * CodeIgniter
 *
 * An open source application development framework for PHP
 *
 * This content is released under the MIT License (MIT)
 *
 * Copyright (c) 2014 - 2015, 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. (http://ellislab.com/)
 * @copyright    Copyright (c) 2014 - 2015, British Columbia Institute of Technology (http://bcit.ca/)
 * @license    http://opensource.org/licenses/MIT    MIT License
 * @link    http://codeigniter.com
 * @since    Version 1.0.0
 * @filesource
 */
defined('BASEPATH') OR exit('No direct script access allowed');

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

/**
 * CodeIgniter Version
 *
 * @var    string
 *
 */
    define('CI_VERSION', '3.0.2');

/*
 * ------------------------------------------------------
 *  Load the framework constants
 * ------------------------------------------------------
 */
    if (file_exists(APPPATH.'config/'.ENVIRONMENT.'/constants.php'))
    {
        require_once(APPPATH.'config/'.ENVIRONMENT.'/constants.php');
    }

    require_once(APPPATH.'config/constants.php');

/*
 * ------------------------------------------------------
 *  Load the global functions
 * ------------------------------------------------------
 */
    require_once(BASEPATH.'core/Common.php');

定义CI_VERSION,引入constants.php、Common.php

ini_set('magic_quotes_runtime', 0);

magic_quotes_runtime

作用:对通过 fread()、file_get_contents() 返回的文本执行 addslashes() 操作,对执行sql查询的结果执行 addslashes() 操作。 作用范围:从文件中读取的数据或执行 exec() 的结果或是从SQL查询中得到的。 作用时间:每次当脚本访问运行状态中产生的数据。
参考地址
参考地址2

/*
 * ------------------------------------------------------
 * Security procedures
 * ------------------------------------------------------
 */

// 小于 5.4 版本存在 register_globals 参数引起的安全问题
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;
                }
            }
        }
    }
}

这一段是为了处理register_globals参数开启带来的安全问题。
register_globals

what-does-egpcs-mean-in-php

/*
 * ------------------------------------------------------
 *  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');

异常处理

/*
 * ------------------------------------------------------
 *  Set the subclass_prefix
 * ------------------------------------------------------
 *
 * 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 a library in the local application
 * "libraries" folder. Since CI allows config items to be
 * overridden via data set in the main index.php file,
 * before proceeding we need to know if a subclass_prefix
 * override exists. If so, we will set this value now,
 * before any classes are loaded
 * Note: Since the config file data is cached it doesn't
 * hurt to load it here.
 */
    if ( ! empty($assign_to_config['subclass_prefix']))
    {
        get_config(array('subclass_prefix' => $assign_to_config['subclass_prefix']));
    }

/*
 * ------------------------------------------------------
 *  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);
        }
    }

/*
 * ------------------------------------------------------
 *  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
 * ------------------------------------------------------
 *
 * 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);
        }
    }

Composer 的配置
引入核心类:Benchmark、Hooks(执行 pre_system hooks)、Config、

/*
 * ------------------------------------------------------
 * 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);
    }

配置charest以及mbstring扩展
官方文档

/*
 * ------------------------------------------------------
 *  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');

/*
 * ------------------------------------------------------
 *  Instantiate the UTF-8 class
 * ------------------------------------------------------
 */
    $UNI =& load_class('Utf8', 'core');

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

/*
 * ------------------------------------------------------
 *  Instantiate the routing class and set the routing
 * ------------------------------------------------------
 */
    $RTR =& load_class('Router', 'core', isset($routing) ? $routing : NULL);

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

/*
 * ------------------------------------------------------
 *    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;
    }

引入 compat下的内容:【待完善】。
引入类Utf8、Router、Output
检测是否需要输出缓存

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

/*
 * ------------------------------------------------------
 *  Load the Input class and sanitize 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_once BASEPATH.'core/Controller.php';

    /**
     * Reference to the CI_Controller method.
     *
     * Returns current CI instance object
     *
     * @return object
     */
    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';
    }

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

/*
 * ------------------------------------------------------
 *  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));
            $method = '_remap';
        }
        // WARNING: It appears that there are issues with is_callable() even in PHP 5.2!
        // Furthermore, there are bug reports and feature/change requests related to it
        // that make it unreliable to use in this context. Please, DO NOT change this
        // work-around until a better alternative is available.
        elseif ( ! in_array(strtolower($method), array_map('strtolower', get_class_methods($class)), TRUE))
        {
            $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);
    }

/*
 * ------------------------------------------------------
 *  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');

/*
 * ------------------------------------------------------
 *  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');