PHP: Create new node inside parent - php

Question

I have a root XML node called and I am trying to add a new child called to this but I am getting errors. Inside there is also children. Here is my code:
$xml = new DomDocument();
$xml->load(X_ASSETS);
$xml->formatOutput = true;
$new_id = $this->getNewAssetId();
// Root
$xpath = new DOMXPath($xml);
$assets = $xpath->query('assets');
$xml_assets = $assets->item(0);
$xml_root = $xml->createElement('asset');
// Asset Name
$xml_name = $xml->createElement('name');
$xml_name->nodeValue = $clean_name;
$xml_root->appendChild($xml_name);
// Asset URL
$xml_url = $xml->createElement('url');
$xml_url->nodeValue = '/'.$name;
$xml_root->appendChild($xml_url);
// Asset ID
$xml_id = $xml->createElement('id');
$xml_id->nodeValue = $new_id;
$xml_root->appendChild($xml_id);
// Create our document and save
$xml_assets->appendChild($xml_root);
$xml->save(X_ASSETS);
I get the following error when running this:
Fatal error: Call to a member function appendChild() on a non-object in /home/websites/zed_x/core/includes/x.inc on line 88
Does anyone know what I am doing wrong here?

Answer 1

Somehow your $xml_assets is not an object, and therefore you cannot call the function:
$xml_assets->appendChild($xml_root);
Are you certain positive that the following command returns an object?
$xml_assets = $assets->item(0);
Test it:
if(is_object($xml_assets))
{
echo "Object Here!";
}
This might be a good way to structure your code so you can catch errors
// .... stuff .....
$xml_assets = $assets->item(0);
// ... more stuff ....
// Check for Object
if(!is_object($xml_assests))
{
die("No Object Created!");
}
$xml_assets->appendChild($xml_root);
$xml->save(X_ASSETS);
// .... more stuff .....