Klarna payment module incopatible with Prestashop 1.4.2.5

We got this error after PrestaShop update from 1.4.17 to 1.4.2.5: “Cart can’t be loaded or an order has already been placed using this cart” and we found the solution to this problem.

PrestaShop changed Cart’s class method from:

public function OrderExists()
{       
 $result = Db::getInstance()->ExecuteS('SELECT `id_cart` FROM `'
._DB_PREFIX_.'orders` WHERE `id_cart` = '.(int)($this->id));
 return Db::getInstance()->NumRows();
}

To:

public function OrderExists()
{
 return (bool)Db::getInstance()->getValue('SELECT `id_cart` FROM `'
._DB_PREFIX_.'orders` WHERE `id_cart` = '.(int)$this->id);

}

As you can see now it returns Boolean value not Integer.

Klarna payment module checks if the order exists with current cart with this line:

$cart->OrderExists() === 0

So now this statement returns false instead of true because variable type is not integer. It returned number of rows in earlier versions  – so 0 means that there was no any order with the current cart and the statement was correct.

You can find this line in file: modules/kreditor/kreditor.php and in modules/cashondeliverywithfee/cashondeliverywithfee.php.

Check these files and change statement from:

$cart->OrderExists() === 0

to:

!$cart->OrderExists()

It will solve the problem.

It’s early morning now and I hope I described this problem clearly. Well I need more coffee. Hope this post saves somebodies time.