PHP pretty print stop working

Question

I have php code that doesn't work anymore

$doc = DOMDocument::loadXML($string);
$doc->formatOutput = true;
echo $doc->saveXML();

I've got error

Fatal error: Call to undefined method stdClass::saveXML() in /path/to/the/File on line 242

I've got PHP version 5.2.14

Answer 1

See the manual on DOMDocument:

If called statically, returns a DOMDocument or FALSE on failure.

and

If an empty string is passed as the source, a warning will be generated. This warning is not generated by libxml and cannot be handled using libxml's error handling functions.

$string is most likely empty.