• http://php.net/manual/en/function.gethostbyaddr.php

    –Note drawbacks of this function… Avoid using system/shell/exec calls.

    http://www.php.net/manual/en/function.dns-get-record.php

    function gethostbyaddr_timeout
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    <?
    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 .= "\1\0\0\1\0\0\0\0\0\0";
    // 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";
    }
    // and the segment itself
    $data .= $bits[$x];
    }
    // and the final bit of the request
    $data .= "\7in-addr\4arpa\0\0\x0C\0\1";
    // create UDP socket
    $handle = @fsockopen("udp://$dns", 53);
    // 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;
    }
    ?>
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