PHP ping

<?php
/// start ping.inc.php ///

$g_icmp_error = "No Error";

// timeout in ms
function ping($host, $timeout)
{
    $port = 0;
    $datasize = 64;
    global $g_icmp_error;
    $g_icmp_error = "No Error";
    $ident = array(ord('J'), ord('C'));
    $seq = array(rand(0, 255), rand(0, 255));

    $packet = '';
    $packet .= chr(8); // type = 8 : request
    $packet .= chr(0); // code = 0

    $packet .= chr(0); // checksum init
    $packet .= chr(0); // checksum init

    $packet .= chr($ident[0]); // identifier
    $packet .= chr($ident[1]); // identifier

    $packet .= chr($seq[0]); // seq
    $packet .= chr($seq[1]); // seq

    for ($i = 0; $i < $datasize; $i++)
        $packet .= chr(0);

    $chk = icmpChecksum($packet);

    $packet[2] = $chk[0]; // checksum init
    $packet[3] = $chk[1]; // checksum init

    $sock = socket_create(AF_INET, SOCK_RAW, getprotobyname('icmp'));
    $time_start = microtime(true);
    socket_sendto($sock, $packet, strlen($packet), 0, $host, $port);


    $read = array($sock);
    $write = NULL;
    $except = NULL;

    $select = socket_select($read, $write, $except, 0, $timeout * 1000);
    if ($select === NULL) {
        $g_icmp_error = "Select Error";
        socket_close($sock);
        return -1;
    } elseif ($select === 0) {
        $g_icmp_error = "Timeout";
        socket_close($sock);
        return -1;
    }

    $recv = '';
    $time_stop = microtime(true);
    socket_recvfrom($sock, $recv, 65535, 0, $host, $port);
    $recv = unpack('C*', $recv);

    if ($recv[10] !== 1) // ICMP proto = 1
    {
        $g_icmp_error = "Not ICMP packet";
        socket_close($sock);
        return -1;
    }

    if ($recv[21] !== 0) // ICMP response = 0
    {
        $g_icmp_error = "Not ICMP response";
        socket_close($sock);
        return -1;
    }

    if ($ident[0] !== $recv[25] || $ident[1] !== $recv[26]) {
        $g_icmp_error = "Bad identification number";
        socket_close($sock);
        return -1;
    }

    if ($seq[0] !== $recv[27] || $seq[1] !== $recv[28]) {
        $g_icmp_error = "Bad sequence number";
        socket_close($sock);
        return -1;
    }

    $ms = bcmul(bcsub($time_stop, $time_start, 6), 1000);

    if ($ms < 0) {
        $g_icmp_error = "Response too long";
        $ms = -1;
    }

    socket_close($sock);

    return $ms;
}

function icmpChecksum($data)
{
    $bit = unpack('n*', $data);
    $sum = array_sum($bit);

    if (strlen($data) % 2) {
        $temp = unpack('C*', $data[strlen($data) - 1]);
        $sum += $temp[1];
    }

    $sum = ($sum >> 16) + ($sum & 0xffff);
    $sum += ($sum >> 16);

    return pack('n*', ~$sum);
}

function getLastIcmpError()
{
    global $g_icmp_error;
    return $g_icmp_error;
}
/// end ping.inc.php ///

使用方法: 

$ping = ping('www.baidu.com',200);
if ($ping > 0) {
    // ok  
} else {
    // failed
}