Php DOM: when setting nodeValue, code is not formatted, literal HTML tags get displayed instead

I am trying to replace one of my div's content:

  $html = new DOMDocument();
    $html->loadHTML($content);

    $elements = $html->getElementsByTagName('div');
    foreach($elements as $element){
      if($element->getAttribute('name') == "left_0"){
       $element->nodeValue = "<h2>Title</h2>";
     }

echo $html-> saveHTML(); 

I get the following output in my index.php:

<h2>Title</h2>

I was looking for an answer, but cant find a way to fix it. Thanks!

In a tag with content like: <h2>Tom</h2>, Tom is the nodeValue and h2 is the nodeName.

You cannot write to nodeName. To create a new node you will have to use this:

$html = new DOMDocument();
$html->loadHTML($content);

$elements = $html->getElementsByTagName('div');
foreach($elements as $element) {
  if ($element->getAttribute('name') == "left_0") {
    $newElement = $html->createElement('h2','Tom'); 
    $element->appendChild($newElement); 
}

If you want to append nested tags, like <p><h2>Title</h2></p> you would do:

$paragraph = $html->createElement('p');         // create outer <p> tag
$currentElement->appendChild($paragraph);       // attach it to parent element
$heading2 = $html->createElement('h2','Title'); // create inner <h2> tag
$paragraph->appendChild($heading2);             // attach that to the <p> tag