Why won't this code work?

Question

I learnt in sololearn that you can include php in html like I did. But it won't work.
https://code.sololearn.com/W9iKVM7OLxkV/?ref=app

Answer 1

that document can not be .html must be .php plus lines 7 and 9 are left over.

Answer 2

You used HTML code editor to include PHP file. And that also in a wrong way.

Use PHP editor,
and you can't include a PHP file here without uploading it to any server and give it's path here.

To include a file, use this syntax-

<?php include "file path with name"; ?>

Answer 3

S.Jaime what do you mean by left over?