codeigniter是如何实现钩子机制的？

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发布时间：2016-07-25 08:46:20

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codeigniter是如何实现钩子机制的？，有需要的朋友可以参考下。

记得上一次去到喜啦面试，面试官问我一个问题：codeigniter是如何实现钩子机制的？
当时答不上来，后来回来之后查了一些资料才明白，所以在这里记录一下：
codeigniter的钩子是这样实现的：首先在框架的核心文件system/core/CodeIniter.php文件的 122行，载入Hooks类，接着在该文件中定义了几个挂载点，比如pre_system（129行）、post_controller_constructor（295行）等，并在这些挂载点上面执行hooks类的_call_hook() 方法。

另附codeigniter的hooks类的源代码：

/**
* CodeIgniter
*
* An open source application development framework for PHP 5.1.6 or newer
*
* @package CodeIgniter
* @author EllisLab Dev Team
* @copyright Copyright (c) 2008 - 2014, EllisLab, Inc.
* @copyright Copyright (c) 2014 - 2015, British Columbia Institute of Technology (http://bcit.ca/)
* @license http://codeigniter.com/user_guide/license.html
* [url=home.php?mod=space&uid=17823]@LINK[/url] http://codeigniter.com
* @since Version 1.0
* @filesource
*/
// ------------------------------------------------------------------------
/**
* CodeIgniter Hooks Class
*
* Provides a mechanism to extend the base system without hacking.
*
* @package CodeIgniter
* @subpackage Libraries
* @category Libraries
* @author EllisLab Dev Team
* @link http://codeigniter.com/user_guide/libraries/encryption.html
*/
class CI_Hooks {
/**
* Determines wether hooks are enabled
*
* @var bool
*/
var $enabled = FALSE;
/**
* List of all hooks set in config/hooks.php
*
* @var array
*/
var $hooks = array();
/**
* Determines wether hook is in progress, used to prevent infinte loops
*
* @var bool
*/
var $in_progress = FALSE;
/**
* Constructor
*
*/
function __construct()
{
$this->_initialize();
log_message('debug', "Hooks Class Initialized");
}
// --------------------------------------------------------------------
/**
* Initialize the Hooks Preferences
*
* @access private
* @return void
*/
function _initialize()
{
$CFG =& load_class('Config', 'core');
// If hooks are not enabled in the config file
// there is nothing else to do
if ($CFG->item('enable_hooks') == FALSE)
{
return;
}
// Grab the "hooks" definition file.
// If there are no hooks, we're done.
if (defined('ENVIRONMENT') AND is_file(APPPATH.'config/'.ENVIRONMENT.'/hooks.php'))
{
include(APPPATH.'config/'.ENVIRONMENT.'/hooks.php');
}
elseif (is_file(APPPATH.'config/hooks.php'))
{
include(APPPATH.'config/hooks.php');
}
if ( ! isset($hook) OR ! is_array($hook))
{
return;
}
$this->hooks =& $hook;
$this->enabled = TRUE;
}
// --------------------------------------------------------------------
/**
* Call Hook
*
* Calls a particular hook
*
* @access private
* @param string the hook name
* @return mixed
*/
function _call_hook($which = '')
{
if ( ! $this->enabled OR ! isset($this->hooks[$which]))
{
return FALSE;
}
if (isset($this->hooks[$which][0]) AND is_array($this->hooks[$which][0]))
{
foreach ($this->hooks[$which] as $val)
{
$this->_run_hook($val);
}
}
else
{
$this->_run_hook($this->hooks[$which]);
}
return TRUE;
}
// --------------------------------------------------------------------
/**
* Run Hook
*
* Runs a particular hook
*
* @access private
* @param array the hook details
* @return bool
*/
function _run_hook($data)
{
if ( ! is_array($data))
{
return FALSE;
}
// -----------------------------------
// Safety - Prevents run-away loops
// -----------------------------------
// If the script being called happens to have the same
// hook call within it a loop can happen
if ($this->in_progress == TRUE)
{
return;
}
// -----------------------------------
// Set file path
// -----------------------------------
if ( ! isset($data['filepath']) OR ! isset($data['filename']))
{
return FALSE;
}
$filepath = APPPATH.$data['filepath'].'/'.$data['filename'];
if ( ! file_exists($filepath))
{
return FALSE;
}
// -----------------------------------
// Set class/function name
// -----------------------------------
$class = FALSE;
$function = FALSE;
$params = '';
if (isset($data['class']) AND $data['class'] != '')
{
$class = $data['class'];
}
if (isset($data['function']))
{
$function = $data['function'];
}
if (isset($data['params']))
{
$params = $data['params'];
}
if ($class === FALSE AND $function === FALSE)
{
return FALSE;
}
// -----------------------------------
// Set the in_progress flag
// -----------------------------------
$this->in_progress = TRUE;
// -----------------------------------
// Call the requested class and/or function
// -----------------------------------
if ($class !== FALSE)
{
if ( ! class_exists($class))
{
require($filepath);
}
$HOOK = new $class;
$HOOK->$function($params);
}
else
{
if ( ! function_exists($function))
{
require($filepath);
}
$function($params);
}
$this->in_progress = FALSE;
return TRUE;
}
}
// END CI_Hooks class
/* End of file Hooks.php */
/* Location: ./system/core/Hooks.php */