PHP Xpath - Parsing flat HTML structure - php

Question

I am trying to parse some fairly flat HTML and group everything from one h1 tag to the next. For example, I have the following HTML:
<h1> Heading 1 </h1>
<p> Paragraph 1.1 </p>
<p> Paragraph 1.2 </p>
<p> Paragraph 1.3 </p>
<h1> Heading 2 </h1>
<p> Paragraph 2.1 </p>
<p> Paragraph 2.2 </p>
<h1> Heading 3 </h1>
<p> Paragraph 3.1 </p>
<p> Paragraph 3.2 </p>
<p> Paragraph 3.3 </p>
I basically want it to look like:
<div id='1'>
<h1> Heading 1 </h1>
<p> Paragraph 1.1 </p>
<p> Paragraph 1.2 </p>
<p> Paragraph 1.3 </p>
</div>
<div id='2'>
<h1> Heading 2 </h1>
<p> Paragraph 2.1 </p>
<p> Paragraph 2.2 </p>
</div>
<div id='3'>
<h1> Heading 3 </h1>
<p> Paragraph 3.1 </p>
<p> Paragraph 3.2 </p>
<p> Paragraph 3.3 </p>
</div>
It is probably not even worth be posting the code I have done so far, as it just turned into a mess. Basically I was attempting to do an Xpath query for '//h1'. Create new DIV tags as parent nodes. Then copy the h1 DOM Node into the first DIV, and then loop over nextSibling until I hit another h1 tag - as mentioned it got messy.
Could someone point me in a better direction here?

Answer 1

Iterate over all nodes that are on the same level (I created a hint node called platau in my example), whenever your run across <h1>, insert the div before and keep a reference to it.
For <h1> and any other node and if the reference exists, remove the node and add it as child to the reference.
Example:
$doc->loadXML($xml);
$xp = new DOMXPath($doc);
$current = NULL;
$id = 0;
foreach($xp->query('/platau/node()') as $i => $sort)
{
if (isset($sort->tagName) && $sort->tagName === 'h1')
{
$current = $doc->createElement('div');
$current->setAttribute('id', ++$id);
$current = $sort->parentNode->insertBefore($current, $sort);
}
if (!$current) continue;
$sort->parentNode->removeChild($sort);
$current->appendChild($sort);
}
Demo