/** * 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 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', '2.1.4'); /** * CodeIgniter Branch (Core = TRUE, Reactor = FALSE) * * @var boolean * */ define('CI_CORE', FALSE); /* * ------------------------------------------------------ * Load the global functions * ------------------------------------------------------ */ require(BASEPATH.'core/Common.php');

這些全域函式讓CI各個元件能整合在一起，卻也導致各元件彼此不可獨立。
（不像Laravel的Eloquent ORM就可以獨立出來使用。）
有沒有辦法避免彼此相依這件事呢？

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

這個地方載入了不同環境下的常數。
注意此處的彈性：可以全部環境共用共一份檔案。

/* * ------------------------------------------------------ * Define a custom error handler so we can log PHP errors * ------------------------------------------------------ */ set_error_handler('_exception_handler'); if ( ! is_php('5.3')) { @set_magic_quotes_runtime(0); // Kill magic quotes } /* * ------------------------------------------------------ * 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 * overriden 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 (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 script execution 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');

載入Hook類別，讓開發者可以在不同時間點執行某些任務，例如：CI載入前、controller執行前、CI執行完畢之後...等等。
Hook類別是提供進階開發者使用的，它的存在主要是為了支援Aspect-Oriented Programming開發方法。
關於在CI內進行AOP開發，我推薦一篇很棒的文章：Explore Aspect Oriented Programming with CodeIgniter

/* * ------------------------------------------------------ * Instantiate the config class * ------------------------------------------------------ */ $CFG =& load_class('Config', 'core'); // Do we have any manually set config items in the index.php file? if (isset($assign_to_config)) { $CFG->_assign_to_config($assign_to_config); } /* * ------------------------------------------------------ * Instantiate the UTF-8 class * ------------------------------------------------------ * * Note: Order here is rather important as the UTF-8 * class needs to be used very early on, but it cannot * properly determine if UTf-8 can be supported until * 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); }

這邊載入Router類別，去分析網址以做出對應動作。
參考：找到該走的路：core/router.php

載入Output類別。它在這份檔案只做兩件事：
1. 有cache時，負責把cache頁面丟給使用者。
2. 沒cache時，負責產出最後ouput的任務。
請參見：回傳最後結果：core/Output.php

/* * ------------------------------------------------------ * Is there a valid 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 class for xss and csrf support * ----------------------------------------------------- */ $SEC =& load_class('Security', 'core');

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

讀取Input類別。在這邊執行建構式的同時，也對PHP的$_GET等變數進行了「消毒」。
參見資訊安全護城河：core/Input.php

/* * ------------------------------------------------------ * 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/'.$CFG->config['subclass_prefix'].'Controller.php'; } // Load the local application controller // Note: The Router class automatically validates the controller path using the router->_validate_request(). // If this include fails it means that the default controller in the Routes.php file is not resolving to something valid. if ( ! file_exists(APPPATH.'controllers/'.$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 $BM->mark('loading_time:_base_classes_end');

載入controller類別，接著定義一個全域函數，可以接觸ci本體物件。
在開發application時，在model、controller等地方會寫到的$this就是繼承這個本體物件。
甚至在撰寫library時，常常為了使用ci本身的helper、model等功能，寫出 $this->ci =& get_instance() 這樣的程式碼。
參見：組裝在一起：core/Controller.php

在core資料夾的類別，幾乎都是用load_class全域函數載入，這邊卻是用require與include。
載入各個類別的機制顯得很混亂。

/* * ------------------------------------------------------ * Security check * ------------------------------------------------------ * * None of the functions in the app controller or the * loader class can be called via the URI, nor can * controller functions that begin with an underscore */ $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? * ------------------------------------------------------ */ $EXT->_call_hook('post_controller_constructor'); /* * ------------------------------------------------------ * Call the requested method * ------------------------------------------------------ */ // Is there a "remap" function? If so, we call it instead if (method_exists($CI, '_remap')) { $CI->_remap($method, array_slice($URI->rsegments, 2)); } else { // is_callable() returns TRUE on some versions of PHP 5 for private and protected // methods, so we'll use this workaround for consistent behavior if ( ! in_array(strtolower($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}/{$method}"); } } // Call the requested method. // Any URI segments present (besides the class/function) will be passed to the method for convenience call_user_func_array(array(&$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? * ------------------------------------------------------ */ $EXT->_call_hook('post_controller'); /* * ------------------------------------------------------ * Send the final rendered output to the browser * ------------------------------------------------------ */ if ($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 */