本文实例讲述了CodeIgniter框架钩子机制实现方法。分享给大家供大家参考，具体如下：

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：

<?php if ( ! defined("BASEPATH")) exit("No direct script access allowed");/** * 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 * @link    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 */

可以看出codeigniter实现钩子机制的方式不够优雅，其实完全可以使用观察者模式来实现钩子机制，将挂载点当做监听的事件。

更多关于CodeIgniter相关内容感兴趣的读者可查看本站专题：《codeigniter入门教程》、《CI(CodeIgniter)框架进阶教程》、《php优秀开发框架总结》、《ThinkPHP入门教程》、《ThinkPHP常用方法总结》、《Zend FrameWork框架入门教程》、《php面向对象程序设计入门教程》、《php+mysql数据库操作入门教程》及《php常见数据库操作技巧汇总》

希望本文所述对大家基于CodeIgniter框架的PHP程序设计有所帮助。