get interface ip by the default gateway on pfsense

get_iface_ip_by_gateway.php

<?php

require_once("interfaces.inc");
require_once("gwlb.inc");

$i = get_interfaces_with_gateway();

$a = shell_exec("netstat -rn | grep -i default | sed -r 's/(.*\ )([0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3})(.*)/\\2/p' | sort -u");
$gw_arr = return_gateways_array();

foreach($gw_arr as $gw)
    if($gw['gateway'] == trim($a))
        print get_interface_ip($gw['friendlyiface']);

?>