Change when the expiration email is sent out for PMPro

my_pmpro_email_expiration.php

<?php
/**
 * Change when the expiration email get's sent out to users.
 *
 * 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_pmpro_email_expiration_date_change( $days ) {

	return 1; // Change this value to the number of days before the expiration date.

}

add_filter( 'pmpro_email_days_before_expiration', 'my_pmpro_email_expiration_date_change' );