Redirect wp-members IPN URL to the PMPro IPN URL

my_ipn_redirect.php

/*
	Redirect wp-members IPN URL to the PMPro IPN URL, e.g.
	https://yoursite.com/?_wpm_gateway=paypal&_wpm_action=ipn =>
	https://yoursite.com/wp-admin/admin-ajax.php?action=ipnhandler
*/
function my_ipn_redirect() {
	if(!empty($_REQUEST['_wpm_gateway']) && !empty($_REQUEST['_wpm_action']) && defined('PMPRO_DIR'))
	{
		if($_REQUEST['_wpm_gateway'] == "paypal" && $_REQUEST['_wpm_action'] == "ipn")
		{
			require_once(PMPRO_DIR . "/services/ipnhandler.php");	
			exit;
		}
	}
}
add_action('init', 'my_ipn_redirect');