OptionalmodeOptionalonCalled after the contribution session is successfully created.
OptionalonCalled if the user closes or cancels the checkout.
OptionalreturnURL to navigate to after a successful redirect-mode checkout.
Appended as ?returnUrl=… to the hosted checkout URL.
How to open the checkout:
redirect— navigate the current tab (default)popup— open in a new browser windowDo not use an iframe/modal — ClickPay blocks framed payment pages.