php - Cannot get user id from session in tank auth codeigniter -

i have controller

<?php if (!defined('basepath')) exit('no direct script access allowed'); error_reporting(e_all); ini_set('display_errors', 1); class response extends ci_controller {     function __construct()     {         parent::__construct();         $this->load->library('tank_auth');      }      function index()     {         $status = $this->input->post('status');         $data['amount'] = $this->input->post('amount');         $data['orderid'] = $this->input->post('orderid');         $data['mobileno'] = $this->input->post('mobileno');         $data['email'] = $this->input->post('email');             echo "userid is".$this->tank_auth->get_user_id();     }  } 

im posting values controller after done,im trying user id session im not able using tank auth.this working in other controllers im having please help