Simple DNSBL/RBL PHP function - trust me, it's better than checkdnsrr, fsock, socket_create, Net::DNSBL and Net::DNS

simple_dnsbl.php

<?php
// Simple DNSBL/RBL PHP function - trust me, it's better than checkdnsrr, fsock, socket_create, Net::DNSBL and Net::DNS
// Here's a [better] way to quickly check if an IP is in a DNSBL / RBL.  It works on Windows and Linux, 
//  assuming nslookup is installed.  It also supports timeout in seconds.

function ipInDnsBlacklist($ip, $server, $timeout=1) {
	$response = array();
	$host = implode(".", array_reverse(explode('.', $ip))).'.'.$server.'.';
	$cmd = sprintf('nslookup -type=A -timeout=%d %s 2>&1', $timeout, escapeshellarg($host));
	@exec($cmd, $response);
	// The first 3 lines (0-2) of output are not the DNS response
	for ($i=3; $i<count($response); $i++) {
		if (strpos(trim($response[$i]), 'Name:') === 0) {
			return true;
		}
	}
	return false;
}

ipInDnsBlacklist('188.163.68.29', 'dnsbl.tornevall.org'); // true
ipInDnsBlacklist('127.0.0.1', 'dnsbl.tornevall.org'); // false
?>

You probably don't have nslookup in your environment.