title: mapping domain name server ip list using any one of the name server ip
body: <p>I'm able to get the nameserver ip by using this code:</p>
  
  <pre><code>$result = exec("host -t NS google.com", $outputLines);
  foreach ($outputLines as $outputLine)
  {
      $buffer = explode(" ", $outputLine);
      $nsList[] = $buffer[3];
  }
  $ipList = array_map("gethostbyname", $nsList);
  print_r($ipList);
  </code></pre>
  
  <p>Now <code>$ipList</code> holds the IP list. Is there any way to get all these IP by inputting any one of the IP in <code>$ipList</code>. </p>
  
  <p>It is like reverse process, I want to get all the IP which <code>$ipList</code> variable holds by inputting any one of the IP present in the <code>$ipList</code> variable.</p>