Session only on private mode

i have been wondering. on a 2.5.2. test envoirment site it seems that sessions ( s::get s::set ) only works within “private mode” across several browsers for me. while another site works fine…

the thing is, there is no error whatsoever, all tasks run like they are supposed to however a session - or session values are not written when i try to dump the sessions contents it returns empty.

without any change i then run a private mode and try it again (my application is some kind of shopping cart) and it works fine.

is there anything i am missing? i have checked my code many times to see if it’s related there …

$session = s::get('cart');

// changed it to make it very simple - as digital product i'll never need to increase qty 
  $session[param('cat')][param('add')] = 1;
  s::set('cart', $session);
  if(empty($session[param('cat')])) unset($session[param('cat')]);
  s::set('cart', $session);


// incognito works fine, normal access doesn't seem to work.
// Result (s::get('cart')) on incognito array(hash)(filenme)
    [pmxo3k] => Array
            [18-55-58.jpg] => 1
            [18-56-58.jpg] => 1

    [13nctcc] => Array
            [0001-20-15-46.jpg] => 1
            [0008-20-19-53.jpg] => 1


on https seems to work, http doesn’t.