Code Igniter user log out after set session array

Question

    $this->session->unset_userdata('transfer_data');
    $quantity = ($_POST['quantity']) ? $_POST['quantity'] : 1;
    $data = array(
        'starting_at' => $_POST['starting_at'],
        'quantity' => $quantity
        );
    $this->session->set_userdata('transfer_data',$data);

After setting $data array active user log in is time out and redirect back to log in screen. How can I prevent this?

Edit :

this log outs happen only when $_POST['starting_at'] array has more data i.e : 200 > with less data it works

Fixed:

Actual problem was not really with that ternary operator but else where it sets session value null I figured and fixed

Answer 1

Fixed:

Actual problem was not really with that ternary operator but else where it sets session value null I figured and fixed