Checking against nameserver is also possible then no considiration of which whois server to use is needed, i wrote this piece of software in a couple of minutes so use it at own risk
PHP Code:
<HTML><HEAD>
<TITLE>DNS Finder</TITLE></HEAD>
<BODY>
<?
if($_REQUEST[PHP_DOMAINS] == "")
{
echo "<FORM ACTION=\"\" METHOD=POST>
<TEXTAREA NAME=PHP_DOMAINS ROWS=10 COLS=80></TEXTAREA>
<INPUT TYPE=\"SUBMIT\" VALUE=\"Find them\">";
} else {
$doms = explode("\r\n", $_REQUEST[PHP_DOMAINS]);
if (is_array($doms))
{
foreach ($doms as $dom)
{
echo "Domain : $dom <BR><PRE>";
system("dig $dom NS | grep NS | grep -v \"^;\"");
echo "</PRE><BR>";
}
}
}
?>
</BODY></HTML>