PHPBuilder has another excerpt posted from the book "PHP 5 in Practice" from Sams Publishing. It takes a quick look at a method to simulate graphical charts with some XHTML and CSS tricks (and PHP's help).

When you need to present data in a chart on a web page, it is often worthwhile to generate graphical charts. This method is covered later in Section 18.4, "Creating a Graph/Chart Library"; however, sometimes for a quick chart CSS can suffice. Listing 9.4.1 presents a function that creates a visual chart of data using CSS and XHTML only.

You can find the code they're talking about for "Listing 9.4.1". They explain it briefly, but it's a quick "here's what it looks like" and less of a "here's the logic behind it" kind of post. Never the less, it's still quite useful.