问上载数据库中的图像和图像名称时出错，codeigniter

EN

      $config['upload_path'] = './assets/Images/profilepictures';
      $config['allowed_types'] = 'gif|jpg|png|jpeg';
      $config['max_size'] = '2048';
      $config['max_width'] = '2000';
      $config['max_height'] = '2000';

      $this->load->library('upload', $config);

      if(!$this->upload->do_upload()){
          $errors = array('error' => $this->upload->display_errors());
          $post_image = 'noimage.jpg';
      } else {
          $data = array('upload_data' => $this->upload->data());
          $post_image = $_FILES['userfile']['name'];
      }

      $this->m_user->profilepicture($post_image);
      if($data['user']->profile_pic==null)
      {
            redirect(base_url().'user/profilepicture/');

      }

    public function profilepicture($post_image){
$userID = $this->session->userdata("user_id");
            $data = array(
            'profile_pic' => $post_image,
            );
      $this->db->where('user_id', $userID);
      $this->db->update('users', $data);
    }