Q:

How to get Product Category name and Category ID on checkout success page?

I am looking for a way to get Category name and Category ID one the checkout success page. So far I have added the product name, sku etc but I am unable to get the category name and id 
Here's my code to product attributes and category names:
<?php //
    $products = array();
    $lastOrderId = Mage::getSingleton('checkout/session')->getLastOrderId();
    $_order = Mage::getSingleton('sales/order')->load($lastOrderId);

/* @var $item Mage_Sales_Model_Order */
foreach ($_order->getAllVisibleItems()  as $item) {
    $info['sku'] = trim($item->getSku());
    $info['qty'] = $item->getQtyOrdered();
    $info['price'] = $item->getPrice();
    $info['name'] = $item->getName();

    $products[] = $info;
}

    $product = Mage::getModel('catalog/product')->load($productId);
    $categoryIds = $product->getCategoryIds();
    $categoryName = '';
if (isset($categoryIds[0])){
    $category = Mage::getModel('catalog/category')->setStoreId(Mage::app()->getStore()->getId())->load($categoryIds[0]);
    $categoryName['category'] = $category->getName();
}

$config['productInfos'] = $products;
$config['cartTotal'] = $_order->getGrandTotal();
$config['currency'] = Mage::app()->getBaseCurrencyCode();
?> 

Here we echo out the values:
_roi.push(['_addItem',
    '<?php echo $product['sku']; ?>', // Merchant SKU
    '<?php echo $product['name']; ?>', // Product Name
    '<?php echo $categoryIds['categoryId']; ?>', // Category ID
    '<?php echo $categoryName['category']; ?>', // Category Name
    '<?php echo $product['price']; ?>', // Unit Price
    '<?php echo $product['qty']; ?>' // Item Quantity
]);

The issue is the CategoryIds and CategoryName are not showing and I'm stuck!
Anyone able to help please do?

A:

$_item['product_id'] is a product id . We will find out categoryid associate with product.
$product = Mage::getModel('catalog/product')->load($_item['product_id']);
$cats = $product->getCategoryIds();

Now we have category ID(s). One product can associate with more then one categorys. This is Magento default nature.  
 foreach ($cats as $category_id) {
    $_cat = Mage::getModel('catalog/category')->setStoreId(Mage::app()->getStore()->getId())->load($category_id);
        echo $_cat->getName();             
    }

$_cat->getName();   is your product category name. This is beneficial if product is associate with a single category. if product is associate with multiple category then we need category ID to get product category name.
i hope this will little helpful for you  

