First, you're on cPanel (not LPCP), and you're using the new File Manager (not the Legacy FM)? What exactly are you seeing when you right-click kittens.php and select View? Keep in mind that's not an editor -- it's a browser (read-only). You should use Edit if you want to change the file (I would avoid the Code Edit, as I've found its behavior to be unpredictable). Don't forget to confirm the character encoding your'e asked.

Once you see all the PHP file and are in a real editor (well, Edit is close enough for minor changes), are you able to make changes and save them, and see the effects in the page? Keep in mind that PHP is a programming language, not the final HTML that your browser renders. You will see little or no HTML in the PHP file. The server interprets this code (programming language) and produces the HTML from it that the browser displays.

Does this answer why you're not seeing what you expect to see? If you don't know PHP but want to play around and learn (with the aid of a book or online course), be sure to back up the files first, and make careful notes of what you're doing so that you can reverse your changes.