Php 访问codeigniter的facebook库中的\u令牌问题

我使用codeigniter框架使用的facebook库在mysite中构建facebook登录

登录工作正常，但最终我看到了这个错误

ERROR - 2013-07-29 06:51:51 --> Severity: Notice  --> Undefined index:  access_token /home/dtworks/public_html/amd/xta2/application/libraries/facebook.php 32

图书馆/facebook.php

 function get_facebook_cookie() {
        $CI = & get_instance();
        $app_id = $CI->config->item('facebook_app_id');
        $application_secret = $CI->config->item('facebook_app_secret');
        if (isset($_COOKIE['fbsr_' . $app_id])) {
            list($encoded_sig, $payload) = explode('.', $_COOKIE['fbsr_' . $app_id], 2);

            $sig = base64_decode(strtr($encoded_sig, '-_', '+/'));
            $data = json_decode(base64_decode(strtr($payload, '-_', '+/')), true);

            if (strtoupper($data['algorithm']) !== 'HMAC-SHA256') {
                return null;
            }
            $expected_sig = hash_hmac('sha256', $payload, $application_secret, $raw = true);
            if ($sig !== $expected_sig) {
                return null;
            }
            $token_url = "https://graph.facebook.com/oauth/access_token?"
                    . "client_id=" . $app_id . "&client_secret=" . $application_secret . "&redirect_uri=" . "&code=" . $data['code'];

            $response = @file_get_contents($token_url);
            $params = null;
            parse_str($response, $params);
            $data['session_key'] = $data['code'];
            $data['access_token'] = $params['access_token'];  // line 32
            return $data;
        } else {
            return null;
        }
    }

控制器/验证其他

// this function to signin with facebook
function fb_signin() {
    // load facebook library
    $this->load->library('facebook'); // this has been loaded in autoload.php
    // get the facebook user and save in the session
    $fb_user = $this->facebook->getUser();
    if (isset($fb_user)) {
        $this->session->set_userdata('facebook_id', $fb_user['id']);

        $user = $this->user_model->get_user_by_sm(array('facebook_id' => $fb_user['id']), 'facebook_id');
        if (sizeof($user) == 0) {
            redirect('auth_other/fill_user_info', 'refresh');
        } else {
            // simulate what happens in the tank auth
            $this->session->set_userdata(array('user_id' => $user[0]->id, 'username' => $user[0]->username,
                'status' => ($user[0]->activated == 1) ? STATUS_ACTIVATED : STATUS_NOT_ACTIVATED));
           // $this->tank_auth->clear_login_attempts($user[0]->email); //can't run this when doing FB
            $this->users->update_login_info($user[0]->id, $this->config->item('login_record_ip', 'tank_auth'), $this->config->item('login_record_time', 'tank_auth'));
            redirect('auth', 'refresh');
        }
    } else {
        echo 'cannot find the Facebook user';
    }
}

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