Return URL behavior. If set to "1" and if a "return" value is submitted, upon completion of the payment the buyer will be sent back to the return URL using a GET method, and no transaction variables will be submitted. If set to "2" and if a "return" value is submitted, the buyer will be sent back to the return URL using a POST method, to which all available transaction variables will also be posted. If omitted or set to "0", GET methods will be used for all Subscriptions transactions and Buy Now, Donations, or PayPal Shopping Cart transactions in which IPN is not enabled. POST methods with variables will be used for the rest.