Call to a member function addChild() on a non-object PHP

Question

I get this error:

Call to a member function addChild() on a non-object

But the XML file looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<urlset>
<url>
  <loc>http://mysite.com/</loc>
  <changefreq>weekly</changefreq>
  <priority>1.00</priority>
</url>
</urlset>

And I'm doing this:

//APPEND TO SITEMAP
$file = '../sitemap.xml';
$xml = simplexml_load_file($file);

$urlset = $xml->urlset;

$urls = $urlset->addChild('url');
$urls->addAttribute("mongoID", $theAuthorUniqueMongoID);
$urls->addChild('loc', 'http://mysite.com/author/'.$authorLink.'/');
$urls->addChild('changefreq', 'monthly');
$urls->addChild('priority', '0.80');

$xml->asXML($file);

I'm basically just appending some stuff to my site map. I was never any good at XML but I'm not sure what I'm doing wrong on this one.

Answer 1

You should change this:

$urlset = $xml->urlset;
$urls = $urlset->addChild('url');

Into:

$urls = $xml->addChild("url");

It will add contents to the root node of the XML you loaded. Thus running the script once yields the following output:

<?xml version="1.0" encoding="UTF-8"?>
<urlset>
  <url>
    <loc>http://mysite.com/</loc>
    <changefreq>weekly</changefreq>
    <priority>1.00</priority>
  </url>
  <url mongoID="">
    <loc>http://mysite.com/author//</loc>
    <changefreq>monthly</changefreq>
    <priority>0.80</priority>
  </url>
</urlset>

I changed the formatting of the output so it was easier to read. The addition is actually just a single line.