Fix #73 item bag error

Author: nfourtythree

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Release Notes for Mollie for Craft Commerce
 
+## Unreleased
+
+- Fixed a PHP error that could occur when making payments. ([#73](https://github.com/craftcms/commerce-mollie/issues/73))
+
 ## 4.4.0 - 2025-06-13
 
 - Molle for Craft Commerce now supports the Klarna payment method. ([#20](https://github.com/craftcms/commerce-mollie/issues/20))

src/gateways/Gateway.php

@@ -10,6 +10,7 @@
 use Craft;
 use craft\base\Event;
 use craft\commerce\base\RequestResponseInterface;
+use craft\commerce\elements\Order;
 use craft\commerce\errors\CurrencyException;
 use craft\commerce\errors\OrderStatusException;
 use craft\commerce\errors\TransactionException;
@@ -36,6 +37,7 @@
 use Omnipay\Common\Message\ResponseInterface;
 use Omnipay\Common\PaymentMethod;
 use Omnipay\Mollie\Gateway as OmnipayGateway;
+use Omnipay\Mollie\Item;
 use Omnipay\Mollie\Message\Request\FetchTransactionRequest;
 use Omnipay\Mollie\Message\Request\PurchaseRequest;
 use Omnipay\Mollie\Message\Response\FetchPaymentMethodsResponse;
@@ -80,6 +82,28 @@ public function getSettings(): array
         return $settings;
     }
 
+    /**
+     * @inheritdoc
+     */
+    protected function createItemBagForOrder(Order $order): ?ItemBag
+    {
+        $itemBag = parent::createItemBagForOrder($order);
+
+        if ($itemBag) {
+            // Morph common `Item`s into `Mollie\Item`s
+            $items = $itemBag->all();
+            foreach ($items as $key => $item) {
+                $items[$key] = new Item($item->getParameters());
+            }
+
+            if (!empty($items)) {
+                $itemBag->replace($items);
+            }
+        }
+
+        return $itemBag;
+    }
+
     /**
      * @param bool $parse
      * @return string|null