[development] Within a conditional action how do I display all the elements within the $order object (dd('order = ' . $order); )?

Within a conditional action custom PHP section I have tried to dump to a log file the contents of the $order object (dd('order = ' . $order);) but it displays nothing but it does display an element within the $order object (dd('order->uid = ' . $order->uid);). Within a conditional action how do I display all the elements within the $order object? Thanks, John