pmpro_payment_option_fields

add_filter('pmpro_payment_option_fields', array('PMProGateway_check', 'pmpro_payment_option_fields'), 10, 2);

pmpro_checkout_preheader

Use this hook to execute code on the checkout page before headers are sent. “Preheader” code runs during the WordPress “init” hook.

do_action( 'pmpro_checkout_preheader' );

pmpro_before_order_list_csv_export

do_action(‘pmpro_before_order_list_csv_export’, $order_ids);

do_action('pmpro_before_order_list_csv_export', $order_ids);