function whois_query($domain) {
  // fix the domain name:
  $domain = strtolower(trim($domain));
  $domain = preg_replace('/^http:\/\//i', '', $domain);
  $domain = preg_replace('/^www\./i', '', $domain);
  $domain = explode('/', $domain);
  $domain = trim($domain[0]);
  // split the TLD from domain name
  $_domain = explode('.', $domain);
  $lst = count($_domain)-1;
  $ext = $_domain[$lst];
  // You find resources and lists 
  // like these on wikipedia: 
  //
  // http://de.wikipedia.org/wiki/Whois
  //
  $servers = array(
    "biz" => "whois.neulevel.biz",
    "com" => "whois.internic.net",
    "us" => "whois.nic.us",
    "coop" => "whois.nic.coop",
    "info" => "whois.nic.info",
    "name" => "whois.nic.name",
    "net" => "whois.internic.net",
    "gov" => "whois.nic.gov",
    "edu" => "whois.internic.net",
    "mil" => "rs.internic.net",
    "int" => "whois.iana.org",
    "ac" => "whois.nic.ac",
    "ae" => "whois.uaenic.ae",
    "at" => "whois.ripe.net",
    "au" => "whois.aunic.net",
    "be" => "whois.dns.be",
    "bg" => "whois.ripe.net",
    "br" => "whois.registro.br",
    "bz" => "whois.belizenic.bz",
    "ca" => "whois.cira.ca",
    "cc" => "whois.nic.cc",
    "ch" => "whois.nic.ch",
    "cl" => "whois.nic.cl",
    "cn" => "whois.cnnic.net.cn",
    "cz" => "whois.nic.cz",
    "de" => "whois.nic.de",
    "fr" => "whois.nic.fr",
    "hu" => "whois.nic.hu",
    "ie" => "whois.domainregistry.ie",
    "il" => "whois.isoc.org.il",
    "in" => "whois.ncst.ernet.in",
    "ir" => "whois.nic.ir",
    "mc" => "whois.ripe.net",
    "to" => "whois.tonic.to",
    "tv" => "whois.tv",
    "ru" => "whois.ripn.net",
    "org" => "whois.pir.org",
    "aero" => "whois.information.aero",
    "nl" => "whois.domain-registry.nl"
  );
  if (!isset($servers[$ext])){
    die('Error: No matching nic server found!');
  }
  $nic_server = $servers[$ext];
  $output = '';
  // connect to whois server:
  if ($conn = fsockopen ($nic_server, 43)) {
    fputs($conn, $domain."\r\n");
    while(!feof($conn)) {
      $output .= fgets($conn,128);
    }
    fclose($conn);
  }
  else { die('Error: Could not connect to ' . $nic_server . '!'); }
  return $output;
}
// Some example queries:
print whois_query('jonasjohn.de');
print whois_query('example.com');
print whois_query('example.org');