There are two different ways to use the PayPal API. The first, is the PayPal Direct Payment. PayPal Direct Payment will allow the customer to simply type in their information including their credit card number and process it invisibly through PayPal on your website. If you use this method, it appears that all orders are being processed without PayPal. The second method is the PayPal Express Checkout.
Coding Library:
PHP
More Paypal Resources:
