Using PayPal Express Checkout

Most payment gateways integrate with OpenGateway so that the users stay on your site and the transactions occur in a one-time API call such as Recur or Charge. However, PayPal Express Checkout requires users to leave your site and enter their PayPal or credit card information on a PayPal check out page. So, by it's nature, this gateway functions a little differently than the others. This documentation covers how Charge and Recur requests differ when using the PayPal Express Checkout gateway.

• Send <return_url> and <cancel_url> elements in the root node of your request.
  return_url should specify the complete web address to refer users to after making their purchase.
  cancel_url should specify the complete web address to refer users to if they choose to abort the payment process.
• You cannot process charges on behalf of others.
  While many integrations of OpenGateway include a virtual terminal where you can enter credit card information and charge a card, PayPal doesn't allow this because, as stated above, the purchasing customer leaves your site to complete payment.
• You should not include a credit_card node in your request, as the user is redirected to PayPal and will enter their payment details there.