86693 Update PHP script

Currently when I add a product with a $0 amount it will add it but still redirects to paypal or credit card payment processor when they buy it. If I add a product with a zero dollar amount I need it to simply perform the operation without redirecting to the payment processor. I posted this job earlier but didn't realize I only had 7 days to pick a programmer and it got closed. So please bid on this project again. Sorry and thanks....