adrianmacneil/omnipay — pull request #65 by philipbrown (2013-05-31 20:39:57+00:00)
Title: Add optional params to WorldPay

A method that allows you to add custom parameters to a WorldPay transaction.

Create a new order with optional params
```php
$gateway = GatewayFactory::create('WorldPay');

$response = $gateway->purchase(array(
"amount"=>"300",
"optional" => array(
"MC_Order" => "order_id",
"MC_Customer" => "customer_id"
)))->send();
```

The method to set optional params
```php
public function setOptional($params)
{
foreach($params as $key => $value)
{
$this->setParameter($key, $value);
}
}
```