php从url获取域名并忽略子域名

Question

i want to get main domain from url. my url:

http://cs541402.vk.me/u170785079/video/l_051000aa.jpg

I want to return: vk.me I tried many ways but not worked for me

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

$url = 'http://cs541402.vk.me/u170785079/video/l_051000aa.jpg';
$url = 'http://' . get_domain($url); 
print get_domain($url);

Answer 1

$url = 'http://vk.me/u170785079/video/l_051000aa.jpg';
$info = parse_url($url);
$host = $info['host'];
$host_names = explode(".", $host);
$bottom_host_name = $host_names[count($host_names)-2] . "." . $host_names[count($host_names)-1];
echo $bottom_host_name;