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출처 :http://cafe.naver.com/2004cash.cafe?iframe_url=/ArticleRead.nhn%3Farticleid=2110
프리랜서를 위한 정보카페

<?
$whois_server = array(
        'com' => 'whois.internic.net',
        'net' => 'whois.internic.net',
        'org' => 'whois.publicinterestregistry.net',
        'co.kr' => 'whois.krnic.net'
);
$whois_avail  = array(
        'whois.internic.net' => 'No match for ',
        'whois.publicinterestregistry.net' => 'NOT FOUND',
        'whois.krnic.net' => 'is not registered to KRNIC'
);

// 도메인 조회 함수
function check_domain( $domain, $suffix ) {
        global $whois_server,$whois_avail;

        $server = $whois_server[$suffix];
        $avail  = $whois_avail[$server];

        // 잘못된 도메인(com,net,org,co.kr이 아닌)
        if (!$server) return false;

        $sock = fsockopen($server,43,$errno,$errstr,30);
        if (!$sock) {
                echo "$errstr [$errno]";
                return false;
        }
        fwrite($sock,"$domain.$suffix\r\n");
        while (!feof($sock)) {
                $ret .= fgets($sock);
        }
        fclose($sock);

        if (strstr($ret,$avail)) return true;
        return false;
}

// 조회 도메인이 있다면
if ($domain) {
        echo "<table cellspacing=0 border=1>\n";
        foreach($whois_server as $suffix => $server) {
                $ret = check_domain($domain,$suffix);
                if ($ret)
                        $OX = 'O';
                else
                        $OX = 'X';
                echo " <tr>\n";
                echo "  <td align=right>$domain.$suffix ($OX)</td>\n";
                echo "  <td> 등록 ";
                if (!$ret) echo "불";
                echo "가능</td>\n";
                echo " </tr>\n";
        }
        echo "</table>\n";
}
?>
<br><br><h3>Domain Search</h3>
<hr size=-1>
<form method=post>
Search Domain : <input type=text name=domain value="<?=$domain?>"><input type=submit value="조회">
</form>