$order = array_map(function ($col) { return $col->seen; }, $users);
# $order = array_column($users, 'seen'); #TODO php7 simplification
array_multisort($order, SORT_DESC, SORT_NUMERIC, $users);
$order = array_map(function ($col) { return $col->seen; }, $users);
# $order = array_column($users, 'seen'); #TODO php7 simplification
array_multisort($order, SORT_DESC, SORT_NUMERIC, $users);