pmpro-recurring-reminder-email-filter-pay-by-check.php

<?php
/**
 * Do not sent recurring payment reminder email if last order gateway is check.
 *
 * This may be useful to stop sending reminder emails to members already receiving
 * pay by check email reminders.
 *
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */

function my_pmprorm_dont_send_reminder_to_pbc( $send_mail, $user, $lastorder ) {

	// Let's only do this if Pay By Check is active.
	if ( ! function_exists( 'pmpropbc_reminder_emails' ) ) {
		return $send_mail;
	}

	// if lastorder gateway is check, return false.
	if ( 'check' === $lastorder->gateway ) {
		return false;
	}

	return $send_mail;
}
add_filter( 'pmprorm_send_reminder_to_user', 'my_pmprorm_dont_send_reminder_to_pbc', 10, 3 );