#!/usr/bin/php
<?php

//PTR nameserver lookup

if (!isset($argv[1])) { exit(); }

$ip = dns_get_record($argv[1], DNS_A);

$ip = explode('.', $ip[0]['ip']);

$reverse_zone = $ip[2] . '.' . $ip[1] . '.' . $ip[0];
$reverse_zone = $reverse_zone . ".in-addr.arpa";

$output = dns_get_record($reverse_zone, DNS_NS);

if (empty($output)) {

    echo "No reverse record set." . PHP_EOL;

} else {

    echo "PTR: ". PHP_EOL . $reverse_zone . PHP_EOL;
    echo "Nameservers:" . PHP_EOL;
    foreach($output as $ns) {
        echo $ns['target'] . PHP_EOL;
    }

}