On the SitePoint PHP blog there's a new post from author Tom Butler that starts from the very beginning and shows you how to write your first PHP code. The article is an excerpt from the SitePoint book PHP & MySQL: Novice to Ninja, 6th Edition.
At this point they assume you've already set up the server to allow for PHP execution. They then provide an example of a HTML page with a bit of PHP that generates a random number. It then gets into some of the basic language syntax and statements and how they're used in the PHP code.