PHP从子域获取域名

print get_domain("http://somedomain.co.uk"); // outputs 'somedomain.co.uk'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;}