未在codeigniter中设置会话

我已经这样设置了会话

$loc_details = array(
                   'maincity_id'  =>$maincity_id,
                   'mainzoneid'     => $mainzoneid,
                   'mainproductid'     => $productid,
               );
        $this->session->set_userdata($loc_details);

$maincity_id=$this->session->userdata('maincity_id');

    //$mainzone_id=$this->session->userdata('mainzone_id');
        $mainproduct_id=$this->session->userdata('mainproductid');

在这里，我检索了如下值

$loc_details = array(
                   'maincity_id'  =>$maincity_id,
                   'mainzoneid'     => $mainzoneid,
                   'mainproductid'     => $productid,
               );
        $this->session->set_userdata($loc_details);

$maincity_id=$this->session->userdata('maincity_id');

    //$mainzone_id=$this->session->userdata('mainzone_id');
        $mainproduct_id=$this->session->userdata('mainproductid');

---

但是如果我看到没有设置会话的输出，有人能帮我吗

$loc_details = array(
               'maincity_id'  =>$maincity_id,
               'mainzoneid'     => $mainzoneid,
               'mainproductid'     => $productid,
           );

 $this->session->set_userdata('loc_details',$loc_details);

 $loc_details = $this->session->userdata("loc_details");

 $maincity_id = $loc_details['maincity_id'];

 $mainproduct_id = $loc_details['mainproductid'];

---

我已经试过了，但是我得到的o/p像这个数组（[maincity_id]=>[mainzoneid]=>[mainproductid]=>plansfr.html）是的，o/p没有得到任何东西，但是对于mainproductid，我得到的是这个plansfr.htmla在您为数组分配了详细信息之后，您可以打印它们并在这里发布输出吗。我是说在你分配任务之前