CartForm::updatecart PHP Method

    public function updatecart($data, $form)
    {
        $items = $this->cart->Items();
        $updatecount = $removecount = 0;
        $request = $this->getRequest();
        $order = ShoppingCart::curr();
        if ($request && $request->isAjax() && $order) {
            ShopTools::install_locale($order->Locale);
        }
        $numericConverter = NumericField::create('_temp');
        $messages = [];
        $badMessages = [];
        if (isset($data['Items']) && is_array($data['Items'])) {
            foreach ($data['Items'] as $itemid => $fields) {
                $item = $items->byID($itemid);
                if (!$item) {
                    continue;
                }
                //delete lines
                if (isset($fields['Remove']) || isset($fields['Quantity']) && (int) $fields['Quantity'] <= 0) {
                    if (ShoppingCart::singleton()->remove($item->Buyable())) {
                        $removecount++;
                    } else {
                        $badMessages[] = ShoppingCart::singleton()->getMessage();
                    }
                    continue;
                }
                //update quantities
                if (isset($fields['Quantity']) && ($quantity = Convert::raw2sql($fields['Quantity']))) {
                    $numericConverter->setValue($quantity);
                    if (!ShoppingCart::singleton()->setQuantity($item->Buyable(), $numericConverter->dataValue())) {
                        $badMessages[] = ShoppingCart::singleton()->getMessage();
                    }
                }
                //update variations
                if (isset($fields['ProductVariationID']) && ($id = Convert::raw2sql($fields['ProductVariationID']))) {
                    if ($item->ProductVariationID != $id) {
                        $item->ProductVariationID = $id;
                    }
                }
                //TODO: make updates through ShoppingCart class
                //TODO: combine with items that now match exactly
                //TODO: validate changes
                if ($item->isChanged()) {
                    $item->write();
                    $updatecount++;
                }
            }
        }
        if ($removecount) {
            $messages['remove'] = _t('CartForm.REMOVED_ITEMS', "Removed {count} items.", "count is the amount that was removed", array('count' => $removecount));
        }
        if ($updatecount) {
            $messages['updatecount'] = _t('CartForm.UPDATED_ITEMS', "Updated {count} items.", "count is the amount that was updated", array('count' => $updatecount));
        }
        if (count($messages)) {
            $form->sessionMessage(implode(" ", $messages), "good");
        }
        if (count($badMessages)) {
            $form->sessionMessage(implode(" ", $badMessages), "bad");
        }
        $this->extend('updateCartFormResponse', $request, $response, $form);
        return $response ? $response : $this->controller->redirectBack();
    }