Obtenir le nom d'hote d'une adresse IP

<?php
//Mesure de perf sur une adresse ip de Google
$t0=microtime(true);
$hostname=@gethostbyaddr('66.249.65.102');
$st=microtime(true)-$t0;
echo "IP 66.249.65.102 <br>nom d'hote :".$hostname."<br>duree :".substr($st,0,4).' sec';
//Mesure de perf sur une adresse ip située en Afrique
$t0=microtime(true);
$hostname=@gethostbyaddr('41.223.184.3 ');
$st=microtime(true)-$t0;
echo "<br>IP 41.223.184.3 <br>nom d'hote :".$hostname."<br>duree :".substr($st,0,4).' sec';
?>

<?php
/**
* Function gethostbyaddr fast resolve Hostname and with Timeout !
*
* @see http://php.net/manual/en/function.gethostbyaddr.php#46869
* @param string $ip IP Address to resolve
* @param string $dns DNS Server IP
* @param int $timeout
* @return string Hostname
*/
function gethostbyaddr_timeout($ip, $dns, $timeout=1000) {
    // random transaction number (for routers etc to get the reply back)
    $data = rand(0, 99);
    // trim it to 2 bytes
    $data = substr($data, 0, 2);
    // request header
    $data .= "11";
    // split IP up
    $bits = explode(".", $ip);
    // error checking
    if (count($bits) != 4) return "ERROR";
    // there is probably a better way to do this bit...
    // loop through each segment
    for ($x=3; $x>=0; $x--) {
        // needs a byte to indicate the length of each segment of the request
        switch (strlen($bits[$x]))
        {
            case 1: // 1 byte long segment
                $data .= "1"; break;
            case 2: // 2 byte long segment
                $data .= "2"; break;
            case 3: // 3 byte long segment
                $data .= "3"; break;
            default: // segment is too big, invalid IP
                return "INVALID";break;
        }
        // and the segment itself
        $data .= $bits[$x];
    }
    // and the final bit of the request
    $data .= "7in-addr4arpa??x0C?1";
    // create UDP socket
    $handle = fsockopen("udp://$dns", 53);
    if (!$handle) {
        return NULL;
    }
    // send our request (and store request size so we can cheat later)
    $requestsize=fwrite($handle, $data);
    socket_set_timeout($handle, $timeout - $timeout00, $timeout00);
    // hope we get a reply
    $response = fread($handle, 1000);
    fclose($handle);
    if ($response == "") {
        return $ip;
    }
    // find the response type
    $type = @unpack("s", substr($response, $requestsize 2));
    if ($type[1] == 0x0C00)  // answer
    {
        // set up our variables
        $host="";
        $len = 0;
        // set our pointer at the beginning of the hostname
        // uses the request size from earlier rather than work it out
        $position=$requestsize 12;
        // reconstruct hostname
        do {
            // get segment size
            $len = unpack("c", substr($response, $position));
            // null terminated string, so length 0 = finished
            if ($len[1] == 0)
            // return the hostname, without the trailing .
            return substr($host, 0, strlen($host) -1);
            // add segment to our host
            $host .= substr($response, $position 1, $len[1]) . ".";
            // move pointer on to the next segment
            $position  = $len[1]   1;
        } while ($len != 0);
        // error - return the hostname we constructed (without the . on the end)
        return $ip;
    }
    return $ip;
}
?>