CI框架中通过hook的方式实现简单的权限控制，cihook_PHP教程

/*
|--------------------------------------------------------------------------
| Enable/Disable System Hooks
|--------------------------------------------------------------------------
|
| If you would like to use the 'hooks' feature you must enable it by
| setting this variable to TRUE (boolean).  See the user guide for details.
|
*/
$config['enable_hooks'] = TRUE;

/*
| -------------------------------------------------------------------------
| Hooks
| -------------------------------------------------------------------------
| This file lets you define "hooks" to extend CI without hacking the core
| files.  Please see the user guide for info:
|
|    http://codeigniter.com/user_guide/general/hooks.html
|
*/
$hook['post_controller_constructor'] = array(
    'class'    => 'Acl',
    'function' => 'auth',
    'filename' => 'acl.php',
    'filepath' => 'hooks'
);

$config['AUTH'] = array(
    SUPER_ADMIN         => array(
        'admin' => array('index', 'logout'),
    ),
    ADMIN   => array(
        'admin' => array('index', 'logout'),
    ),
    GUEST => array(
        'admin' => array('index', 'logout'),
    ),
);

class Acl {
    private $url_model;
    private $url_method;
    private $CI;
    function Acl()
    {
        $this->CI =& get_instance();
        $this->CI->load->library('session');
        $this->url_model = $this->CI->uri->segment(1);
        $this->url_method = $this->CI->uri->segment(2);
    }
    function auth()
    {
        $user = $this->CI->session->userdata('USER');
        if(empty($user))
            $user->status = 0;
        $this->CI->load->config('acl');
        $AUTH = $this->CI->config->item('AUTH');
        if(in_array($user->status, array_keys($AUTH))){
            $controllers = $AUTH[$user->status];
            if(in_array($this->url_model, array_keys($controllers))){
                if(!in_array($this->url_method, $controllers[$this->url_model])){
                    show_error('您无权访问该功能，该错误已经被记录！点击返回');
                }
            }else{
                show_error('您无权访问该模块，该错误已经被记录！点击返回');
            }
        }
        else
            show_error('错误的用户类型，该错误已经被记录！点击返回');
    }
}

$this->CI =& get_instance();