Passing variables to another page - newbie

I have an order form that is validating input, mailing me the results of the form, then I want to pass the user off to either Paypal or Revecom (depending on their choice) for processing. Everything works except trying to pass the variables to the payment processor. I thought that header("location://url?var1=value1?var2=value2") would work but not luck. Could someone point me in the right direction please? Thanks, Dean Martin