Google Analytics ecommerce tracking in Magento

<?php
$order = Mage::getModel('sales/order')->load(Mage::getSingleton('checkout/session')->getLastOrderId()); 
$subtotal = $order->getSubtotal();
$order_id = $order->getId(); //the id of the order
//$order->getIncrementId();//the increment id of the order
$gtotal = $order->getGrandTotal();//grand total of the order 
$address = $order->getBillingAddress()->getData();
$city = $address['city'];
$state = $address['region'];
$country = $address['country_id'];
?>
<script type="text/javascript">
ga('require', 'ecommerce');

ga('ecommerce:addTransaction', {
  'id': '<?php echo $order_id; ?>',                     // Transaction ID. Required.
  'affiliation': '',   // Affiliation or store name.
  'revenue': '<?php echo $gtotal;?>',               // Grand Total.
  'shipping': '0',                  // Shipping.
  'tax': '0'                     // Tax.
});

<?php 
$items = $order->getAllItems();
$itemcount=count($items);
$name=array();
$unitPrice=array();
$sku=array();
$ids=array();
$qty=array();
foreach ($items as $itemId => $item)
{?>
ga('ecommerce:addItem', {
  'id': '<?php echo $order_id; ?>',                     // Transaction ID. Required.
  'name': '<?php echo $item->getName(); ?>',    // Product name. Required.
  'sku': '<?php echo $item->getSku(); ?>',                 // SKU/code.
  'category': '',         // Category or variation.
  'price': '<?php echo $item->getPrice(); ?>',                 // Unit price.
  'quantity': '<?php echo $item->getQtyToInvoice(); ?>'                   // Quantity.
});
<?php 
}
?> 
ga('ecommerce:send');

</script>