ip6.biz/src/hostname.php

<?php
header('Content-Type: application/json');

$ip = $_SERVER['REMOTE_ADDR'];
if (substr($ip, 0, 9) === "10.23.42.") {
	$ip = "88.99.139.92";
}

$ip = escapeshellcmd($ip);

print(json_encode(gethost($ip)));

function gethost($ip)
{
	$ires = array();

	$host = `host -s -W 5 $ip`;
	$host = explode(' ', trim(trim($host), '.'));
	$host = ($host ? end($host) : $ip);
	$ires = array();
	if(in_array($host, Array('reached', 'record', '3(NXDOMAIN)')))
	{
		$ires["status"] = "none";
	}
	else if (in_array( $host, Array('2(SERVFAIL)'))){
		$ires["status"] = "servfail";
	}
	else
	{
		$ires["status"] = "ok";
		$ires["response"] = $host;
	}

	return $ires;
}