Facebook PHP API：getUser返回0

Question

将Codeigniter框架与Facebook的PHP SDK和Javascript SDK结合使用。 这是我的代码。

public function __construct(){
            parent::__construct();
            $this->load->library('session');   
            $this->config->load('facebook');
            $this->load->library('Facebook',array('appId'=>$this->config->item('appID'),'secret'=>$this->config->item('appSecret')));

    }
function fblogin(){
        $base_url=$this->config->item('base_url');
        $user = $this->facebook->getUser();
        log_message('info','>>>>>>>>>>>>User id is::'.$this->config->item('appID').'::'.$this->config->item('appSecret').' For session '.session_id());
        if($user == 0){

            $loginUrl = $this->facebook->getLoginUrl(array("scope"=>"user_about_me"));
            redirect("$loginUrl","location");

        }
        if($user){
            try{
                $user_profile = $facebook->api('/me');
                $params = array('next' => $base_url.'fbci/logout');
                $ses_user=array('User'=>$user_profile,
                   'logout' =>$facebook->getLogoutUrl($params)
                );
                $this->session->set_userdata($ses_user);
                redirect('/','refresh');
                header('Location: '.$base_url);
            }catch(FacebookApiException $e){
                log_message('error',error_log($e));
                $user = NULL;
            }       
        }

的Javascript

FB.login(function(response) {
          console.log('fb respone'+response.serialize());
          if(response.authResponse) {
              parent.location ="<?php echo site_url('fbci/fblogin');?>";
          }
      },{scope: 'email,read_stream,publish_stream,user_birthday,user_location,user_work_history,user_hometown,user_photos'});
    });

在libraries文件夹中添加了Facebook.php和base_facebook.php。这段代码看起来很直接，但没有弄错。