How to prevent self closing tag in php simplexml

Question

I want to generate xml by using php simplexml.

$xml = new SimpleXMLElement('<xml/>');

$output = $xml->addChild('child1');
$output->addChild('child2', "value");
$output->addChild('noValue', '');

Header('Content-type: text/xml');
print($xml->asXML());

The output is

<xml>
   <child1>
      <child2>value</child2>
      <noValue/>
   </child1>
</xml>

What I want is if the tag has no value it should display like this

<noValue></noValue>

I've tried using LIBXML_NOEMPTYTAG from Turn OFF self-closing tags in SimpleXML for PHP?

I've tried $xml = new SimpleXMLElement('<xml/>', LIBXML_NOEMPTYTAG); and it doesn't work. So I don't know where to put the LIBXML_NOEMPTYTAG

Answer 1

Despite the quite lengthy answers already given - which are not particularly wrong and do shed some light into some libxml library internals and it's PHP binding - you're most likely looking for:

$output->noValue = '';

To add an open tag, empty node-value and end tag (beautified, demo is here: http://3v4l.org/S2PKc):

<?xml version="1.0"?>
<xml>
  <child1>
    <child2>value</child2>
    <noValue></noValue>
  </child1>
</xml>

Just noting as it seems it has been overlooked with the existing answers.