pmpro_payment_option_fields


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

pmpro_gateways


add_filter( 'pmpro_gateways', array( 'PMProGateway_check', 'pmpro_gateways' ) );