Do I need a !DOCTYPE declaration in a php file with html?

Question

I have a php file with my website content in it. The file needs to be .php because i get some variables first and then use it later in the website content. Like this example

Answer 1

PHP really has nothing to do with HTML - it's just the server-side code spitting out a bunch of text that the browser interprets.

A doctype is a critical part of how the browser interprets the HTML that follows.