$re = '~^[0-9\p{L}][0-9\p{L}-\.]{1,61}[0-9\p{L}]\.[0-9\p{L}][\p{L}-]*[0-9\p{L}]+$~um';
$str = 'google.com
masełkowski.pl
maselkowski.pl
m.maselkowski.pl
www.masełkowski.pl.com
xn--masekowski-d0b.pl
中国互联网络信息中心.中国
masełkowski.pl.
masełk..owski.pl
中国互联网络信息中心.xn--masekowski-d0b
';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php