<?php
$nodes = array("node1.example.com", "node2.example.com", "node3.example.com");
foreach($nodes as $node) {

$ping = exec("ping -c 1 ".$node); 
if (strpos($ping, '0 received') === false) { 
    echo $node." is reachable  

";

} else { 
    echo $node." is unreachable  

";

}                                                   } ?>