Payment configuration for SilverStripe

_config.php

<?php

/*
 * Payment
 * ====================================================
 */

//Order notifications sent to
Email::setAdminEmail('test@example.com');

Payment::set_supported_methods(array(
  'PayPalExpressCheckoutPayment' => 'PayPal Express'
));

PayPalExpressCheckoutPayment::set_config_details(
  'username', 
  'password', 
  'signature'
);
PayPalPayment::set_account_email('test@example.com');