Get authorize.net transaction code into GA tracking

<?php
// originally from Alex in Help Scout 20 February 2013
add_filter("gform_confirmation", "custom_confirmation", 10, 4);
function custom_confirmation($confirmation, $form, $lead, $ajax){
    if($form["id"] == "102"){
        $transaction_id = GFAuthorizeNet::$transaction_response["transaction_id"];
        $confirmation .= "<script type='text/javascript'>

var _gaq = _gaq || [];
_gaq.push(['_setAccount', 'UA-2360178-80']);
_gaq.push(['_trackPageview']);
_gaq.push(['_addTrans','{$transaction_id}', // transaction ID - required
'American Knight Promotion', // affiliation or store name
'{Total:24}', // total - required
'0', // tax
'0', // shipping
'{Address (City):28.3}', // city
'{Address (State / Province):28.4}', // state or province
'USA' // country
]);

// add item might be called for every item in the shopping cart
// where your ecommerce engine loops through each item in the cart and
// prints out _addItem for each
_gaq.push(['_addItem', '{$transaction_id}', // transaction ID - required
'978-0-9882148-0-4', // SKU/code - required
'Return to Order - Hardcover', // product name
'Hard cover', // category or variation
'{Return to Order - Hardcover (Price):26.2}', // unit price - required
'{Return to Order - Hardcover (Quantity):26.3}' // quantity - required
]);
_gaq.push(['_trackTrans']); //submits transaction to the Analytics servers

(function() {
var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
})();

</script>";
    }

    return $confirmation;
}