gethostbynamel

Description

array gethostbynamel ( string hostname )

Returns a list of IP addresses to which the Internet host specified by hostname resolves. Returns FALSE if hostname could not be resolved.

例子 1. gethostbynamel() example


<?php
  $hosts = gethostbynamel('www.example.com');
  print_r($hosts);
?>

The printout of the above program will be:

Array
(
    [0] => 192.0.34.166
)

See also gethostbyname(), gethostbyaddr(), checkdnsrr(), getmxrr(), and the named(8) manual page.

add a note User Contributed Notes

mitch <> aka-root.com
08-Feb-2006 09:23


Bug found in versions php4.4.0-4.4.2 (no newest in 4.4.x when i write this)



if domain does not exist, gethostbyname retourn local server ip, in 4.3.x branch in this case retourn equal input string.



u can check it by this simple code :)



<?

$str = 'any-not-valid-domain.com';

$ip4 = gethostbyname($str);

print "[$str] [$ip4]<br>";

?>

webdev at concraption dot com
20-Sep-2005 02:25


In PHP 5.0.4, gethostbynamel returns an empty string instead of false if the lookup fails. A simple workaround for this error is to use is_array() in an IF block:



<?

$hosts = gethostbynamel($hostname);

if (is_array($hosts)) {

     echo "Host ".$hostname." resolves to:<br><br>";

     foreach ($hosts as $ip) {

          echo "IP: ".$ip."<br>";

     }

} else {

     echo "Host ".$hostname." is not tied to any IP.";

}

?>

php at silisoftware dot com
04-Dec-2004 09:39


This is a replacement for gethostbynamel(), for *nix only, which uses the "host" program to lookup hostnames. Most people won't need this, but I had a temporary server problem where all the PHP DNS lookup functions were failing, so this works as a direct replacement:



function SafeGetHostByNameL($hostname) {

    if (false) { // put conditional check here to use normal gethostbynamel()

        return gethostbynamel($hostname);

    } elseif (ereg('[0-9]{1,3}(\.[0-9]{1,3}){3}', $hostname)) {

        return array($hostname);

    } else {

        $response = trim(`host $hostname`);

        if (preg_match_all('/([a-z0-9\.\-]* is an alias for ([a-z0-9\.\-]*)\.['." \r\n".']+)*[a-z0-9\.\-]* has address ([0-9]+\.[0-9]+\.[0-9]+\.[0-9]+)/', trim($response), $matches, PREG_PATTERN_ORDER)) {

            return $matches[3];

        } elseif (eregi('^Host '.$hostname.' not found', $response, $matches)) {

            return false;

        }

    }

    return false;

}

Skyld at o2 dot co dot uk
25-Sep-2004 04:45


Obviously, in some cases, not all IPs are likely to be useful while checking a hostname. Sometimes also, not all IPs will work. This code will check for the first WORKING IP from the list. Or at least it should - I haven't had time to test it yet.

Needs domain parameter, and port and max IPs to check are optional.

If port is not set, it will check HTTP port 80, and if max IPs to check is not set, it will only check the first 10 IPs from the list.

Hope it helps someone.



<?php

  function checkhostlist($domain, $port = 80, $maxipstocheck = 10) {

   $hosts = gethostbynamel($domain);

    for ($chk=0;$chk<$maxipstocheck;$chk++) {

      if (isset($hosts[$chk])) {

        $th = fsockopen($domain, $port);

        if ($th) {

          fclose($th);

          return $hosts[$chk];

          break;

        }

      }

    }

  }

?>

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