private function storeOrderItems($order, $data)
    {
        $cart = isset($data['num_cart_items']);
        $numItems = (isset($data['num_cart_items'])) ? $data['num_cart_items'] : 1;

        for ($i = 0; $i < $numItems; $i++) {

            $suffix = ($numItems > 1 || $cart) ? ($i + 1) : '';
            $suffixUnderscore = ($numItems > 1 || $cart) ? '_' . $suffix : $suffix;

            $item = new IpnOrderItem();
            if (isset($data['item_name' . $suffix]))
                $item->item_name = $data['item_name' . $suffix];
            if (isset($data['item_number' . $suffix]))
                $item->item_number = $data['item_number' . $suffix];
            if (isset($data['quantity' . $suffix]))
                $item->quantity = $data['quantity' . $suffix];
            if (isset($data['mc_gross' . $suffixUnderscore]))
                $item->mc_gross = $data['mc_gross' . $suffixUnderscore];
            if (isset($data['mc_handling' . $suffix]))
                $item->mc_handling = $data['mc_handling' . $suffix];
            if (isset($data['mc_shipping' . $suffix]))
                $item->mc_shipping = $data['mc_shipping' . $suffix];
            if (isset($data['tax' . $suffix]))
                $item->tax = $data['tax' . $suffix];

            $order->items()->save($item);

            // Set the order item options if any
            // $count = 7 because PayPal allows you to set a maximum of 7 options per item
            // Reference: https://cms.paypal.com/us/cgi-bin/?cmd=_render-content&content_ID=developer/e_howto_html_Appx_websitestandard_htmlvariables
            for ($ii = 1, $count = 7; $ii < $count; $ii++) {
                if (isset($data['option_name' . $ii . '_' . $suffix])) {
                    $option = new IpnOrderItemOption();
                    $option->option_name = $data['option_name' . $ii . '_' . $suffix];
                    if (isset($data['option_selection' . $ii . '_' . $suffix])) {
                        $option->option_selection = $data['option_selection' . $ii . '_' . $suffix];
                    }
                    $item->options()->save($option);
                }
            }
        }
    }