by Kerafym on Tue Jun 12, 2012 1:39 pm
HTML has changed quite a bit. Unless you learned CSS with HTML, your knowledge is probably obsolete. However, it's pretty easy to pick up the new standards and everything if you're already comfortable with the syntax. It took me 2-3 days to completely re-learn HTML with CSS when I did some web design about 4 or 5 years ago.
PHP is a bit different from HTML and CSS. It's a bit more like programming. Think of HTML and CSS as what controls the layout; this color here, a table with these dimensions there, if you will. While you CAN directly put content into your HTML page; it will be static every single time the page loads. This means that, until you manually change the HTML or CSS file, the page will load exactly the same every time.
If you want dynamically changing content, you're going to need something a bit more advanced than HTML and CSS. PHP is one of these options, and it can do a lot of different things. For example, in the case of these forums, it pulls data from a database to display all of the posts associated with each thread. HTML and CSS cannot do this, however PHP can. PHP takes all of this information and creates a dynamic webpage with all of the information from each of the posts in the thread.
PHP is pretty much only web based, so I wouldn't really call it "programming" as much as just web design, but it is partially based on a couple of different "real" programming languages, so if you learn PHP it'd be easy-ish to transition to something like C++, Java, etc.