caption element changes

      // Center aligned content requires an additional wrapper to set
      // text-align: center.
      if ($align === 'center') {

        // If the image has a caption
        $caption = $node->getAttribute('data-caption');
        if ($caption) {
          // something like this, but in PHP
          // element.replaceWith(figure);
          // figure.add(element);
          // figure.add(caption);
        }
        else {
          
          // Get closest p parent.
          while ($target->nodeName !== 'p') {
            $target = $target->parentNode;
          }

          $p_attribute = $dom->createAttribute('class');
          $p_attribute->value = 'centered-wrapper';
          $target->appendChild($p_attribute);
        }

      }