Allow performing actions just before sending the user to the gateway to complete the payment.

do_action( 'pmpro_before_commit_express_checkout', $order );

Parameters

$order

MemberOrder object; The new order with status = token.

Source

File: https://github.com/strangerstudios/paid-memberships-pro/blob/master/classes/gateways/class.pmprogateway_paypalexpress.php