Aqui les dejo uno que encontre:
<?php
$status = $_GET['status'];
$host = $_GET['host'];
$host = trim($host);
$host = strtolower($host);
$ip = $_SERVER['REMOTE_ADDR'];
$self = $_SERVER['PHP_SELF'];
if ( $status == "whois" )
{
if( !(ereg("[a-z0-9\-\_.]+\.[a-z]{2,5}$", $host)))
{
echo '<br><br>';
echo "<span class=\"black\"><u>$host</u> El nombre de dominio no parece ser valido.</span><br><br>";
echo '<input type="button" value=" Back &nb sp; " onClick="window.history.back()">';
echo '</div></body></html>';
exit();
}
echo("<span class=\"plainBlue\">Whois del Dominio: <u>$host</u></span><br>");
echo '<div align="left">';
echo '<pre>';
system ("whois $host");
echo '</pre>';
echo '</div>';
} else {
?>
<table border="0" width="300">
<tr>
<td align="center" colspan="2">
<span class="plainBlue">Your IP is: <?php echo $ip; ?></span>
<form method="get" action="<?php echo $self; ?>">
</td></tr>
<tr><td height="20" colspan="2"></td></tr>
<tr>
<td align="left"><span>Enter IP or Hostname : </span></td>
<td align="left"><input type="text" name="host"></input></td>
</tr>
<tr><td height="15" colspan="2"></td></tr>
<tr>
<td height="25" colspan="2" align="left">
<input type="hidden" name="status" value="whois">
<input type="submit" name="submit" value=" Whois &n bsp; " class="black"></td>
</tr>
<tr><td height="25"></td></tr>
<tr>
<td align="left" colspan="2">
<p class="white"> </p>
</td>
</tr>
</form>
</table><br>
<?php
}
if( $status == "whois" )
{
echo '<input type="button" class="black" value="<<< Regresar" onClick="window.location=\''.$self.'\'"><br><br>';
}
?>