$dom = $_SERVER["HTTP_HOST"];

function getDomain($url) {
  $pieces = parse_url($url);
  $domain = $pieces['path'];
  if (preg_match('/(?P<domain>[a-z0-9][a-z0-9\-]{1,63}\.[a-z\.]{2,6})$/i', $domain, $regs)) {
    return $regs['domain'];
  }
  return false;
}


$domain_adi = getDomain($dom);