Ecco uno script trovato in rete.
codice:
    <?php

    /*

    	example: page.php?s=yahoo.it

    */

    $server = array(

    "asia" => "whois.nic.asia",

    "biz" => "whois.biz",

    "com" => "whois.verisign-grs.com",

    "coop" => "whois.nic.coop",

    "info" => "whois.afilias.net",

    "jobs" => "jobswhois.verisign-grs.com",

    "mobi" => "whois.dotmobiregistry.net",

    "name" => "whois.nic.name",

    "net" => "whois.verisign-grs.com",

    "org" => "whois.pir.org",

    "pro" => "whois.registrypro.pro",

    "tel" => "whois.nic.tel",

    "travel" => "whois.nic.travel",

    "gov" => "whois.dotgov.gov",

    "edu" => "whois.educause.edu",

    "int" => "whois.iana.org",

    "museum" => "whois.museum",

    "ac" => "whois.nic.ac",

    "ae" => "whois.nic.ae",

    "ag" => "whois.nic.ag",

    "am" => "whois.amnic.net",

    "at" => "whois.nic.at",

    "au" => "whois.aunic.net",

    "be" => "whois.dns.be",

    "bg" => "whois.register.bg",

    "bj" => "whois.nic.bj",

    "br" => "whois.registro.br",

    "ca" => "whois.cira.ca",

    "ch" => "whois.nic.ch",

    "ci" => "whois.nic.ci",

    "cl" => "whois.nic.cl",

    "cn" => "whois.cnnic.net.cn",

    "cx" => "whois.nic.cx",

    "cz" => "whois.nic.cz",

    "de" => "whois.denic.de",

    "dk" => "whois.dk-hostmaster.dk",

    "ee" => "whois.eenet.ee",

    "fi" => "whois.ficora.fi",

    "fr" => "whois.nic.fr",

    "gd" => "whois.adamsnames.com",

    "gg" => "whois.channelisles.net",

    "gi" => "whois2.afilias-grs.net",

    "gs" => "whois.nic.gs",

    "gw" => "whois.nic.gw",

    "gy" => "whois.registry.gy",

    "hk" => "whois.hkirc.hk",

    "hn" => "whois2.afilias-grs.net",

    "ie" => "whois.domainregistry.ie",

    "il" => "whois.isoc.org.il",

    "in" => "whois.inregistry.net",

    "io" => "whois.nic.io",

    "ir" => "whois.nic.ir",

    "is" => "whois.isnic.is",

    "it" => "whois.nic.it",

    "je" => "whois.channelisles.net",

    "jp" => "whois.jprs.jp",

    "ke" => "whois.kenic.or.ke",

    "kg" => "www.domain.kg",

    "ki" => "whois.nic.ki",

    "kr" => "whois.nic.or.kr",

    "kz" => "whois.nic.kz",

    "la" => "whois.nic.la",

    "li" => "whois.nic.li",

    "lt" => "whois.domreg.lt",

    "lu" => "whois.dns.lu",

    "lv" => "whois.nic.lv",

    "ly" => "whois.nic.ly",

    "ma" => "whois.iam.net.ma",

    "mg" => "whois.nic.mg",

    "mn" => "whois.nic.mn",

    "ms" => "whois.adamsnames.tc",

    "mx" => "whois.nic.mx",

    "my" => "whois.mynic.net.my",

    "na" => "whois.na-nic.com.na",

    "nl" => "whois.domain-registry.nl",

    "no" => "whois.norid.no",

    "nu" => "whois.nic.nu",

    "nz" => "whois.srs.net.nz",

    "pl" => "whois.dns.pl",

    "pm" => "whois.nic.pm",

    "pr" => "whois.uprr.pr",

    "re" => "whois.nic.re",

    "ro" => "whois.rotld.ro",

    "ru" => "whois.ripn.net",

    "sa" => "whois.nic.net.sa",

    "sb" => "whois.nic.net.sb",

    "sc" => "whois2.afilias-grs.net",

    "se" => "whois.iis.se",

    "sg" => "whois.nic.net.sg",

    "sh" => "whois.nic.sh",

    "si" => "whois.arnes.si",

    "st" => "whois.nic.st",

    "tc" => "whois.adamsnames.tc",

    "tf" => "whois.nic.tf",

    "tk" => "whois.dot.tk",

    "tl" => "whois.nic.tl",

    "tm" => "whois.nic.tm",

    "tr" => "whois.nic.tr",

    "tw" => "whois.twnic.net.tw",

    "ua" => "whois.net.ua",

    "ug" => "whois.co.ug",

    "uk" => "whois.nic.uk",

    "us" => "whois.nic.us",

    "uz" => "whois.cctld.uz",

    "vc" => "whois2.afilias-grs.net",

    "ve" => "whois.nic.ve",

    "vg" => "whois.adamsnames.tc",

    "wf" => "whois.nic.wf",

    "ws" => "whois.website.ws",

    "yt" => "whois.nic.yt");

     

    $s = getDomain($_GET['s']);

     

    if($s != NULL && $server[$s[1]] != "") {

    	$connection = fsockopen($server[$s[1]], 43);

    	if (!$connection)

    		echo "Errore";

    	else {

    		$msg = "";

    		fputs($connection, $s[0].".".$s[1]."\r\n"); 

    		while (!feof($connection))

    			$msg .= fgets($connection, 4096);

     

    		fclose($connection);

     

    		echo "<pre>".

    			$msg

    		."</pre>";

    	}

    }else 

    	echo "URL non valido";

     

    function getDomain($url) {

    	$arrU = explode(".", $url);

    	if(count($arrU) >= 2)

    		return array($arrU[count($arrU)-2], $arrU[count($arrU)-1]);

    	else

    		return NULL;

    }

    ?>
Comunque se cerchi "whois script php" ne trovi diversi.
Saluti
Davide