The Net_Whois query method uses $this to refer to the instantiated object.  Since you're attempting to call the method statically there is no instantiation to reference and hence the parses sees:

$whoisData = NULL->_connect($whoisServer, $domain);

which obviously makes no sense.

Instantiate the class, then call the method via your newly created object.

when I modify to this,
$whoisData = NULL->_connect($whoisServer, $domain);

it's still have problem like this,
Parse error: parse error, unexpected T_OBJECT_OPERATOR in /home/local/lib/php/Net/Whois.php on line 131

Fatal error: Undefined class name 'net_whois' in /home/richliu/public_html/test/whoistest.php on line 12

Example Have problem :<

$whois = new Net_Whois;
$data = whois->query("poorman.org");
echo $data;

Please be careful about the code you write, you forgot a $

$whois = new Net_Whois;
$data = $whois->query("poorman.org");
        ^
echo $data;

<?php
require_once "../Net/Whois.php";

$query  = "softgrid.in";     // get information about
$whois = new Net_Whois;
$data = $whois->query($query);
echo $data;

?>

The code runs fine, but not formatted. Anyone got the well arranged solution??