Check if the PC is alone in the network

aloneInTheNetwork.php

#!/usr/bin/php5 -q
<?php
$broadcast = "10.55.2.255";
$ignore = array('10.55.2.240','10.55.2.66');
$ignore = implode('|',$ignore);
$string = "ping -b {$broadcast} -c 2 | grep 'icmp_req=1' | grep -vE '{$ignore}'";
$result = shell_exec($string);
if (trim($result))
{
	exit('false');
}
exit('true');