Codeigniter使用HOOK

Question

如何在codeigniter中使用hook？

我有config / hooks.php

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

$hook['post_controller_constructor'] = array(
        'class'    => 'init',
        'function' => 'start',
        'filename' => 'init.php',
        'filepath' => 'hooks',
        'params'   => array('index')
);

然后是init.php

class init {

    function start() {
        if(strtolower($_SERVER['REQUEST_METHOD']) == 'options') die();
        $ci =& get_instance();
        $session = $ci->load->library('session');
        $tokenAuth = $ci->load->library('tokenAuth');
    }
}

如何检查会话或tokenAuth。如果存在??? 感谢。