Well, how familiar are you with HTML, MySQL, (or any other db lang), and CSS? In the end, a PHP file is really just parsed HTML, so anything not between <?php and ?> is just good ole markup. It also depends on what you want to get out of it, since PHP covers so much ground, but given that PHP is more attractive from the back than the front, I'll assume you wanna build some server-side applications. So for starters, in order to familiarize yourself with $_POST and $_GET (the two variables you'll be molesting the most) and the basic syntax try doing some simple HTML pages that evaluates some browser/platform condition and slowly work your way into HTML forms and attempt a feedback form. After that you'll work your way into MySQL functions and how to evaluate their output (this is back-back-end stuff [your typical db commands; creates, queries, inserts, etc]), user authentication comes next along with the global variable $_SESSION, which also considers how to handle cookies and different types of users, and lastly, after you've completed all of the following, you could attempt some sort of CMS (keep in my mind the scale since you're still learning), but by creating a basic CMS you'll slowly start seeing what an MVC pattern is in PHP. It's hardly abstract and quite hideous since you're only using MySQL and PHP, but by participating in this process you should uncover the gist of PHP and why it's so easy. After that if you're still sane, install PEAR and reiterate the process using their libraries else if unsatisfied or overwhelmed move onto something in Java and try JavaServer Pages.
