html - Change page title with PJAX? -

I am using PJX with Cake PHP. Everything works great, but since I am not loading the layout again, I do not get a headline update. I was told that I had to put a tag in the body and it would be removed. It seems to work, but is it a valid HTML page without tags?

EDIT: Well the tag is not actually removed, so the HTML markup is invalid! What is the best practice for this? It should be similar to Metas.

The official demo uses it in Ruby but I can not read it:

Since PXX also shows a data attribute data-title in the loaded section and should update the main title.

It is very clean and does not break with title in body .