Note that I'm not trying to answer Ahundiak's ?? to Jimson, just throwing in my two-pence...
Content is text and images, generally coded in HTML.
Presentation, these days, is coded in CSS --- and it's cool. No matter where in the file I put the text or image tags, as long as the CSS is set correctly and the div or id tags are around the content, it shows up in the right place. "position: absolute;" is about the coolest thing I've learned in the last coupla years --- besides PHP....
PHP is the logic... when something has to happen besides spewing 'content' in the same old manner, you use PHP (server side) or JS (client side)....
FWIW, I'm an old phart, without enough math, science, and logic to fill a teakettle; basically my larger scripts are long lists of functions, many of which just include HTML "content", followed by a short script that lays the logic out in the fewest lines possible...otherwise, PHP just sits in the HTML and "activates" the content, like it was intended to do....