I' have website design but now I want to code it, I have good knowledge of HTML / HTML5 and CSS, but little in PHP. My question is how can I start coding my website with PHP do I actually code the entire website with PHP or combined?

What I think is I would start to layer out each page with HTML and CSS and after that I move on to PHP, creating login system, and other dynamic website functions and after that I styling each page.

Please correct me if I am wrong this is my first attempt in creating something serious.