How to add nested tags to dom?
$item = $dom->createElement('Level1');
$items->appendChild($item);
$field = $item->appendChild($dom->createElement('Level3'));
$field->appendChild($dom->createTextNode('23'));
<Level1>
<!-- Hot to add sub tag of Level2
<Level3>23</Level3>
</Level1>
to be like
<Level1>
<Level2>
<Level3>23</Level3>
</Level2>
</Level1>
