PS 1.6.1.8 | Impossible to get order_id

[spirit_infernal]

Hello everyone. 
I want to get id_order for further usage, but after few attempts have no luck with it. 

public static function getIdOrder($id_cart)
    {
        return Db::getInstance()->executeS(
            'SELECT id_order FROM '._DB_PREFIX_.'orders WHERE id_cart = '.$id_cart
        );
    }

this function return bool(true), if I set executeS($sql, false, false) it return only string like 'SELECT id_order FROM ps_orders, WHERE id_cart = 4701', not id_order.

Different apporoaches found across internet give same results. For example, using 

$order_object = new OrderCore();
$idOrder = $order_object->getOrderByCartId((int)($mycart->id));;

return same bool(true), but not ID. All theese actions are doing for programmatically update order_detail, which oesn't accept sql update injections without id_order.

Hope someone help me. Thanks in advance

[jgamio]

Change the

 

executeS by GetValue

 

execute is going to return array not a value

[spirit_infernal]

thanks, will try

[spirit_infernal]

still return bool(false) with following:

public static function getIdOrder($id_cart)
    {
        return Db::getInstance()->GetValue(
            'SELECT id_order FROM '._DB_PREFIX_.'orders WHERE id_cart = '.$id_cart
        );
    }

 

[spirit_infernal]

thanks jgamio. Your suggestion works like a charm. My fault was where I tried to use this function - before cart really creates.