删除php中的xml节点

my xml file:

<temporary>
  <users>
    <temp>
      <id>1</id>
      <title> Undercover</title>
      <author>Wiwit</author>
    </temp>
    <nissi>
      <confirm>3977678bce8515e8cdbfa64850904ad1</confirm>
      <firstname>hi</firstname>
      <lastname>hhey</lastname>
      <day>1</day>
    </nissi>
   </users>
</temporary>

my php:

<?php
$user="nissi";
$xml = simplexml_load_file("temporary.xml") 
       or die("Error: Cannot create object");
unset($xml->temporary->users->$user);
?>

Why is this not working. The unset is not working.The node ins'nt getting deleted.

It works like this :

$user="nissi";
$xml = simplexml_load_file("temporary.xml") 
       or die("Error: Cannot create object");
unset($xml->users->$user);
echo $xml->asXML();

You mustn't take the root of your xml in the "request" temporary here.

DEMO HERE

You cannot do it with SimpleXML alone, you have to use DOMElement conversion as explained here:

Remove a child with a specific attribute, in SimpleXML for PHP