Laravel/Omnipay paypal, pass custom shipping amount - php

Question

I'm trying pass a custom shipping price to paypal express checkout.
I'm using omnipay and laravel 4.
I gather this is possible as referenced in the paypal express docs but cant get it to work with omnipay Ive tried the following:
/*set api details*/
$request = $gateway->purchase([
'amount'=> $cart['total'],
'currency' => 'GBP',
'XXX' => 100
'transactionId' => $order->reference,
'returnUrl' => $returnURL . '/checkout/success',
'cancelUrl' => $returnURL . '/checkout/cancel'
])->setItems($cart['items'])->send();
/*handleResponse*/
where XXX is shipping, shippingAmt, shipping_amount, I've tried adding shipping value to each item in the cart. I've tried modifying abstractrequest.php class to add on a shipping value manually like so:
protected function getItemData()
{
$data = array();
$items = $this->getItems();
if ($items) {
foreach ($items as $n => $item) {
$data["L_PAYMENTREQUEST_0_NAME$n"] = $item->getName();
$data["L_PAYMENTREQUEST_0_DESC$n"] = $item->getDescription();
$data["L_PAYMENTREQUEST_0_QTY$n"] = $item->getQuantity();
$data["L_PAYMENTREQUEST_0_AMT$n"] = $this->formatCurrency($item->getPrice());
}
}
$data["L_PAYMENTREQUEST_0_SHIPPINGAMT"] = "3.00";
return $data;
}

Answer 1

I found the answer here
I was using an older version of package, so just needed to run composer update and could use the function setShippingAmount();