> PHP came about in the era of server-side includes, and expecting it to have grokked the DOM structure out of the box is just hindsight.

Obviously not from the beginning. But by the time template frameworks like Twig came around it should have been possible. If it can be done at runtime it's possible to build into the language proper. And I'm specifically talking about the time when PHP 7 started taking other features from Hack.

I'm not grinding an axe here, i'm just stating an opinion.