I would like to rewrite my website from Google sites to HTML. I have some knowledge of PHP, but I would like to use Netfly which is a free host but does not support PHP. So, is there a line of HTML to include PHP?
You have a fundamental misunderstanding somewhere.
A CDN is a service that provides geographically localised, static files that browsers can download quickly.
PHP, in the context of the WWW, is a server-side programming language. It is never delivered to browsers. It can’t be included by a line of HTML.
Consequently, the idea of a CDN for PHP doesn’t make any sense.