New on the phpPro site is this article looking at a technique for embedding PHP inside of your CSS files and have it correctly interpreted.

Perhaps one of the most frustrating aspects of using PHP with websites, is getting variables into CSS. Having variables stored in an ini file, config file or even a database can make the updating of the look and feel of a site simple, however, CSS files, by default, do not parse PHP. [...] A html file may also include a PHP file, in the same manner as it includes a CSS file. This means the stylesheet can be renamed from style.css to style.php.

Using this method, the PHP inside the file is parsed and, because its included with a link tag, the CSS is also made available to the rest of the page.