Updating XML node with PHP

Question

I've an XML file test.xml

<?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>

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

<?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";
?>

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.

Answer 1

You're not accessing the right node. In your example, $xml holds the root node <info/>. Here's a great tip: always name the variable that holds your XML document after its root node, it will prevent such confusion.

Also, as Ward Muylaert pointed out, you need to save the file.

Here's the corrected example:

// load the document
// the root node is <info/> so we load it into $info
$info = simplexml_load_file('test.xml');

// update
$info->user->name->nameCoordinate->xName = $xPostName;
$info->user->name->nameCoordinate->yName = $yPostName;

// save the updated document
$info->asXML('test.xml');

Answer 2

You have to write the changes back to the file, use the asXML method of the SimpleXMLElement.