Get productID from specific order in Magento

$order = Mage::getModel('sales/order')->load($order_id);

$items = $order->getAllItems();

$itemcount=count($items);

$name=array();

$unitPrice=array();

$sku=array();

$ids=array();

$qty=array();

foreach ($items as $itemId => $item)

{

    $name[] = $item->getName();

    $unitPrice[]=$item->getPrice();

    $sku[]=$item->getSku();

    $ids[]=$item->getProductId();

    $qty[]=$item->getQtyToInvoice();

}