src/Cart/ShoppingCart.php
public function archiveorderid($requestedOrderId = null)
    {
        $session = ShopTools::getSession();
        $sessionId = $session->get(self::config()->cartid_session_name);
        $order = Order::get()
            ->filter('Status:not', 'Cart')
            ->byId($sessionId);

        if ($order && !$order->IsCart()) {
            OrderManipulationExtension::add_session_order($order);
        }
        // in case there was no order requested
        // OR there was an order requested AND it's the same one as currently in the session,
        // then clear the cart. This check is here to prevent clearing of the cart if the user just
        // wants to view an old order (via AccountPage).
        if (!$requestedOrderId || ($sessionId == $requestedOrderId)) {
            $this->clear();
        }
    }
public function archiveorderid($requestedOrderId = null)
    {
        $session = ShopTools::getSession();
        $sessionId = $session->get(self::config()->cartid_session_name);
        $order = Order::get()
            ->filter('Status:not', 'Cart')
            ->byId($sessionId);

        if ($order && !$order->IsCart()) {
            OrderManipulationExtension::add_session_order($order);
        }
        // in case there was no order requested
        // OR there was an order requested AND it's the same one as currently in the session,
        // then clear the cart. This check is here to prevent clearing of the cart if the user just
        // wants to view an old order (via AccountPage).
        if (!$requestedOrderId || ($sessionId == $requestedOrderId)) {
            $this->clear();
        }
    }
Store old cart id in session order history

@param int|null $requestedOrderId optional parameter that denotes the order that was requested