PHP CodeIgniter框架的工作原理研究

PHP编程
<?php
//*BASEPATH/system/core/Common.php
 //引导文件中Benchmark,Hooks,Config等都是通过这个函数进行加载的
 function &load_class($class,$directory = 'libraries',$prefix = 'CI_')
 {
  //记录加载过的类
  static $_classes = array();
  // 已经加载过,直接读取并返回
  if (isset($_classes[$class]))
  {
   return $_classes[$class];
  }
  $name = FALSE;
  // 在指定目录寻找要加载的类
  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;
   }
  }
  // 没有找到
  if ($name === FALSE)
  {
   exit('Unable to locate the specified class: '.$class.'.php');
  }
  // 追踪记录下刚才加载的类,is_loaded()函数在下面
  is_loaded($class);
  $_classes[$class] = new $name();
  return $_classes[$class];
 }
 // 记录已经加载过的类.函数返回所有加载过的类
 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;
  
  //将所有在引导文件中(CodeIgniter.php)初始化的类对象(即刚才4,5,6,7,8,9等步骤),//注册成为控制器类的成员变量,就使得这个控制器成为一个超级对象(super object)
  foreach (is_loaded() as $var => $class)
  {
   $this->$var =& load_class($class);
  }
<span style="white-space:pre">  </span>//加载Loader对象,再利用Loader对象对程序内一系列资源进行加载<span style="white-space:pre"> </span>
  $this->load =& load_class('Loader','core');
  $this->load->initialize();
  
  log_message('debug',"Controller Class Initialized");
 }
 //这个函数对外提供了控制器的单一实例
 public static function &get_instance()
 {
  return self::$instance;
 }
}
//*BASEPATH/system/core/CodeIgniter.php
 // Load the base controller class
 require BASEPATH.'core/Controller.php';
 //通过这个全局函数就得到了控制器的实例,得到了这个超级对象,//意味着在程序其他地方调用这个函数,就能得到整个框架的控制权
 function &get_instance()
 {
  return CI_Controller::get_instance();
 }
 // 加载对应的控制器类
 // 注意：Router类会自动使用 router->_validate_request() 验证控制器路径
 if ( ! file_exists(APPPATH.'controllers/'.$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 = $RTR->fetch_method(); //action name
 //.....
 // 调用哀求的函数
 // uri中除了class/function之外的段也会被传递给调用的函数
 call_user_func_array(array(&$CI,$method),array_slice($URI->rsegments,2));
 //输出最终的内容到浏览器
 if ($EXT->_call_hook('display_override') === FALSE)
 {
  $OUT->_display();
 }
 
//*BASEPATH/system/core/Loader.php
 //看一个Loader类加载model的例子.这里只列出了部分代码
 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);
  //依次根据model类的path进行匹配,如果找到了就加载
  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);
   //这里依然将model对象注册成控制器类的成员变量.Loader在加载其他资源的时候也会这么做
   $CI->$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()是一个魔术方法,当读取一个未定义的变量的值时就会被调用
 //如下是Model基类对__get()函数的一个实现,使得在Model类内,可以像直接在控制器类内一样(例如$this->var的方式)去读取它的变量
 function __get($key)
 {
  $CI =& get_instance();
  return $CI->$key;
 }