IP to ISP/Country/City (GeoIP) using PHP

I've noted that many people are searching here about how to find out City/Country/ISP details from IP; often referred as GeoIP. Here, I've compiled my replies that once I posted to comp.lang.php

Get the IP

Refer http://www.iana.org/assignments/ipv4-address-space/ipv4-address-space.xml and see which whois server should be used for the whois lookup

Now, do the whois lookup. e.g., whois -h whois.apnic.net 61.x.x.x

Parse the results. AFAIK, it will have the ISP, City and Country info

For whois lookup, may use rwhois protocol through below PHP code:



<?php
function whois($host, $command)
{
  $fp = fsockopen ($host, 43, $errno, $errstr, 100);
  if (!$fp) {
     $result = $errstr . $errno . "\n";
  } else {
    fputs ($fp, $command . "\r\n\r\n");
    $result = '';
    while (!feof($fp)) {
      $result .= fgets ($fp, 128);
    }
    fclose ($fp);
  }
  return $result;
}

//debug...
echo whois('whois.internic.net', 'php.net');
?>