Convert Zurb Foundation Accordion to generic details/summary using DomDocument

convertfoundationAccordion.php

<?php

$input = 'Some text<a href="#">Test</a><ul class="accordion" data-accordion role="tablist">
  <li class="accordion-navigation" role="presentation">
    <a href="#panel1d" role="tab" id="panel1d-heading" aria-controls="panel1d">Accordion 1</a>
    <div id="panel1d" class="content active" role="tabpanel" aria-labelledby="panel1d-heading">
      Panel 1. Lorem ipsum dolor
    </div>
  </li>
  <li class="accordion-navigation" role="presentation">
    <a href="#panel2d"  role="tab" id="panel2d-heading" aria-controls="panel2d">Accordion 2</a>
    <div id="panel2d" class="content" role="tabpanel" aria-labelledby="panel2d-heading">
      Panel 2. Lorem ipsum dolor<a href="#">foo</a>
    </div>
  </li>
  <li class="accordion-navigation" role="presentation">
    <a href="#panel3d" role="tab" id="panel3d-heading" aria-controls="panel3d">Accordion 3</a>
    <div id="panel3d" class="content" role="tabpanel" aria-labelledby="panel3d-heading">
      Panel 3. Lorem ipsum dolor
    </div>
  </li>
</ul>';

$input2 = 'Some text<a href="#">Test</a><ul class="accordion" data-accordion="">
<li class="accordion-navigation"><a href="#citations" aria-expanded="false">Citations</a><div>
<pre class="content" id="citations"><sup>1 Texas Department of Family and Protective Services. Family First Prevention Act. Retrieved from https://www.dfps.state.tx.us/Child_Protection/Family_First/default.asp
2 Chen, E., Brody, G. H., &amp; Miller, G. E. (2017). Childhood close family relationships and health. The American psychologist, 72(6), 555–566. Retrieved from https://doi.org/10.1037/amp0000067
</pre></div></li>
<li class="accordion-navigation"><a href="#pdf" aria-expanded="false">PDF Version</a><br>
<div class="content" id="pdf">test<a href="/sites/default/files/CFRPBrief_B0440121_SupportingPregnantandParentingTeensinCare.pdf" target="_blank">Supporting Pregnant and Parenting Teens in Care with Home Visiting (PDF)</a></div>
</li>
</ul>';

function appendHTML(DOMNode $parent, $source) {
    $tmpDoc = new DOMDocument();
    $tmpDoc->loadHTML($source);
    foreach ($tmpDoc->getElementsByTagName('body')->item(0)->childNodes as $node) {
        $node = $parent->ownerDocument->importNode($node, true);
        $parent->appendChild($node);
    }
}

function DOMinnerHTML(DOMNode $element) { 
  $innerHTML = ""; 
  $children  = $element->childNodes;
  foreach ($children as $child) { 
    $innerHTML .= $element->ownerDocument->saveHTML($child);
  }
  return $innerHTML;
} 

function convertFoundationAccordion($text) {
  $original = $text;
  // LibXML requires that the html is wrapped in a root node.
  $text = '<root>' . $text . '</root>';
  $dom = new \DOMDocument();
  $dom->preserveWhiteSpace = FALSE;
  libxml_use_internal_errors(TRUE);
  $dom->loadHTML(mb_convert_encoding($text, 'HTML-ENTITIES', 'UTF-8'), LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD);
  $uls = $dom->getElementsByTagName('ul');
  if ($uls->length === 0) {
    return $original;
  }
  foreach ($uls as $ul) {
    $classes = $ul->getAttribute('class');
    if (strpos($classes, 'accordion') === FALSE) {
      continue;
    }
    $lis = $ul->getElementsByTagName('li');
    if ($lis->length === 0) {
      continue;
    }
    $convert = TRUE;
    $content = '';
    $titleObjects = [];
    $bodyObjects = [];
    foreach ($lis as $key => $li) {
      if (!$convert) {
        continue;
      }
      $classes = $li->getAttribute('class');
      if (strpos($classes, 'accordion-navigation') === FALSE) {
        continue;
      }
      $titleObjects[$key] = $li->getElementsByTagName('a');
      $bodyObjects[$key] = $li->getElementsByTagName('div');
      if ($bodyObjects[$key][0] && $titleObjects[$key][0]) {
        if (isset($bodyObjects[$key][0]->nodeValue) && isset($titleObjects[$key][0]->nodeValue)) {
          $content .= '<details><summary>' . $titleObjects[$key][0]->nodeValue . '</summary>' . DOMInnerHTML($bodyObjects[$key][0]) . '</details>';
        }
        else {
          $convert = FALSE;
        }
      }
      else {
        $convert = FALSE;
      }
    }
    if ($convert) {
      $elem = $dom->createElement('div');
      appendHTML($elem, $content);
      $ul->parentNode->replaceChild($elem, $ul);
    }
  }
  // Get innerHTML of root node.
  $html = "";
  foreach ($dom->getElementsByTagName('root')->item(0)->childNodes as $child) {
    // Re-serialize the HTML.
    $html .= $dom->saveHTML($child);
  }
  return $html;
}

$output = convertFoundationAccordion($input);

print_r($output);