Updating XML node with PHP

[Eric]

I've an XML file test.xml\[code\]<?xml version="1.0"?><info> <user> <name> <firstname>FirstName</firstname> <lastname>Last Name</lastname> <nameCoordinate> <xName>125</xName> <yName>20</yName> </nameCoordinate> </name> </user></info>\[/code\]I'm trying to update the node xName & yName using PHP on a form submission. So, I've loaded the file using simplexml_load_file(). The PHP form action code is below\[code\]<?php $xPostName = $_POST['xName']; $yPostName = $_POST['yName']; //load xml file to edit $xml = simplexml_load_file('test.xml'); $xml->info->user->name->nameCoordinate->xName = $xPostName; $xml->info->user->name->nameCoordinate->yName = $yPostName; echo "done";?>\[/code\]I want to update the node values but the above code seems to be incorrect. Can anyone help me rectify it??UPDATE:My question is somewhat similar to this Updating a XML file using PHP but here, I'm loading the XML from an external file and also I'm updating an element, not an attribute. That's where my confusion lies.