Location from ip address

Question

Do you know of any service which given an ip address it returns a location/country? I found a few lists we can add to our database but do I need to update them often? Is there any rule (like telephone numbers) to know the country of origin?

Sorry, I know this might sound a stupid question but for what we're doing it can't fail.

EDIT: I forgot to mention this has to be accessible programmatically (PHP)

Thanks :) Diogo

Answer 1

Check this out: http://www.farhad.ca/2011/06/15/rbl-based-ip-to-location/

Assume IP address of question is 10.11.12.13, then here is a sample:

<?php

$ip_address = gethostbyname('13.12.11.10.rbloc.dayanadns.com');
list($d1,$d2,$d3,$d4) = explode('.',$ip_address);
$country_code = chr($d3).chr($d4);

print "Result address: ".$ip_address."\n";
print "Country code: ".$country_code."\n";

?>