PHP DOMDocument: what is the nicest way to safely add text to an element

Question

When adding a string that might contain troublesome characters (eg &, <, >), DOMDocument throws a warning, rather than sanitizing the string.

I'm looking for a succinct way to make strings xml-safe - ideally something that leverages the DOMDocument library.

I'm looking for something better than preg_replace or htmlspecialchars. I see DOMDocument::createTextNode(), but the resulting DOMText object is cumbersome and can't be handed to DOMDocument::createElement().

To illustrate the problem, this code:

<?php 

$dom = new DOMDocument;
$dom->formatOutput = true;
$parent = $dom->createElement('rootNode');
$parent->appendChild( $dom->createElement('name', 'this ampersand causes pain & sorrow ') );
$dom->appendChild( $parent );
echo $dom->saveXml();

produces this result (see eval.in):

Warning: DOMDocument::createElement(): unterminated entity reference          sorrow in /tmp/execpad-41ee778d3376/source-41ee778d3376 on line 6
<?xml version="1.0"?>
<rootNode>
  <name>this ampersand causes pain </name>
</rootNode>

Answer 1

You will have to create the text node and append it. I described the problem in this answer: https://stackoverflow.com/a/22957785/2265374

However you can extend DOMDocument and overload createElement*().

class MyDOMDocument extends DOMDocument {

  public function createElement($name, $content = '') {
    $node = parent::createElement($name);
    if ((string)$content !== '') {
      $node->appendChild($this->createTextNode($content));
    }
    return $node;
  }

  public function createElementNS($namespace, $name, $content = '') {
    $node = parent::createElementNS($namespace, $name);
    if ((string)$content !== '') {
      $node->appendChild($this->createTextNode($content));
    }
    return $node;
  }
}

$dom = new MyDOMDocument();
$root = $dom->appendChild($dom->createElement('foo'));
$root->appendChild($dom->createElement('bar', 'Company & Son'));
$root->appendChild($dom->createElementNS('urn:bar', 'bar', 'Company & Son'));

$dom->formatOutput = TRUE;
echo $dom->saveXml();

Output:

<?xml version="1.0"?>
<foo>
  <bar>Company &amp; Son</bar>
  <bar xmlns="urn:bar">Company &amp; Son</bar>
</foo>