如何将属性添加到xml节点？

I generating following xml in php.

PHP Code :-

header("Content-type: text/xml");
echo "<?xml version='1.0' encoding='UTF-8'?>";
echo "<Response>";
echo "<Dial>";
echo  $client_no;
echo "</Dial>";
echo "<Say>The call failed or the remote party hung up. Goodbye.</Say>";
echo "</Response>";

Output :-

<Response>
  <Dial>919880022477</Dial>
  <Say>
      The call failed or the remote party hung up. Goodbye.
  </Say>
</Response>

now i want to add attribute to the Dial node. something like :-

<Dial callerId="jitu">919880022477</Dial>

try this

echo "<Dial callerID='jitu'>";