PHP編程
<?php
//*BASEPATH/system/core/Common.php
 //引導文件中Benchmark,Hooks,Config等都是通過這個函數進行加載的
 function &load_class($class, $directory = 'libraries', $prefix = 'CI_')
 {
  //記錄加載過的類
  static $_classes = array();
  // 已經加載過,直接讀取并返回
  if (isset($_classes[$class]))
  {
   return $_classes[$class];
  }
  $name = FALSE;
  // 在指定目錄尋找要加載的類
  foreach (array(APPPATH, BASEPATH) as $path)
  {
   if (file_exists($path.$directory.'/'.$class.'.php'))
   {
    $name = $prefix.$class;
    if (class_exists($name) === FALSE)
    {
     require($path.$directory.'/'.$class.'.php');
    }
    break;
   }
  }
  // 沒有找到
  if ($name === FALSE)
  {
   exit('Unable to locate the specified class: '.$class.'.php');
  }
  // 追蹤記錄下剛才加載的類,is_loaded()函數在下面
  is_loaded($class);
  $_classes[$class] = new $name();
  return $_classes[$class];
 }
 // 記錄已經加載過的類.函數返回所有加載過的類
 function &is_loaded($class = '')
 {
  static $_is_loaded = array();
  if ($class != '')
  {
   $_is_loaded[strtolower($class)] = $class;
  }
  return $_is_loaded;
 }
//*BASEPATH/system/core/Controller.php
class CI_Controller {
 private static $instance;
 public function __construct()
 {
  self::$instance =& $this;
  
  //將所有在引導文件中(CodeIgniter.php)初始化的類對象(即剛才4,5,6,7,8,9等步驟),
  //注冊成為控制器類的成員變量,就使得這個控制器成為一個超級對象(super object)
  foreach (is_loaded() as $var => $class)
  {
   $this->$var =& load_class($class);
  }
<span style="white-space:pre">  </span>//加載Loader對象,再利用Loader對象對程序內一系列資源進行加載<span style="white-space:pre"> </span>
  $this->load =& load_class('Loader', 'core');
  $this->load->initialize();
  
  log_message('debug', "Controller Class Initialized");
 }
 //這個函數對外提供了控制器的單一實例
 public static function &get_instance()
 {
  return self::$instance;
 }
}
//*BASEPATH/system/core/CodeIgniter.php
 // Load the base controller class
 require BASEPATH.'core/Controller.php';
 //通過這個全局函數就得到了控制器的實例,得到了這個超級對象,
 //意味著在程序其他地方調用這個函數,就能得到整個框架的控制權
 function &get_instance()
 {
  return CI_Controller::get_instance();
 }
 // 加載對應的控制器類
 // 注意：Router類會自動使用 router->_validate_request() 驗證控制器路徑
 if ( ! file_exists(APPPATH.'controllers/'.$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');
 $class = $RTR->fetch_class(); //Controller class name
 $method = $RTR->fetch_method(); //action name
 //.....
 // 調用哀求的函數
 // uri中除了class/function之外的段也會被傳遞給調用的函數
 call_user_func_array(array(&$CI, $method), array_slice($URI->rsegments, 2));
 //輸出最終的內容到瀏覽器
 if ($EXT->_call_hook('display_override') === FALSE)
 {
  $OUT->_display();
 }
 
//*BASEPATH/system/core/Loader.php
 //看一個Loader類加載model的例子.這里只列出了部分代碼
 public function model($model, $name = '', $db_conn = FALSE)
 {
  $CI =& get_instance();
  if (isset($CI->$name))
  {
   show_error('The model name you are loading is the name of a resource that is already being used: '.$name);
  }
  $model = strtolower($model);
  //依次根據model類的path進行匹配,如果找到了就加載
  foreach ($this->_ci_model_paths as $mod_path)
  {
   if ( ! file_exists($mod_path.'models/'.$path.$model.'.php'))
   {
    continue;
   }
   if ($db_conn !== FALSE AND ! class_exists('CI_DB'))
   {
    if ($db_conn === TRUE)
    {
     $db_conn = '';
    }
    $CI->load->database($db_conn, FALSE, TRUE);
   }
   if ( ! class_exists('CI_Model'))
   {
    load_class('Model', 'core');
   }
   require_once($mod_path.'models/'.$path.$model.'.php');
   $model = ucfirst($model);
   //這里依然將model對象注冊成控制器類的成員變量.Loader在加載其他資源的時候也會這么做
   $CI->$name = new $model();
   $this->_ci_models[] = $name;
   return;
  }
  // couldn't find the model
  show_error('Unable to locate the model you have specified: '.$model);
 }
//*BASEPATH/system/core/Model.php
 //__get()是一個魔術方法,當讀取一個未定義的變量的值時就會被調用
 //如下是Model基類對__get()函數的一個實現,使得在Model類內,可以像直接在控制器類內一樣(例如$this->var的方式)去讀取它的變量
 function __get($key)
 {
  $CI =& get_instance();
  return $CI->$key;
 }