Yes ... or rather it's the start of my style sheet file. If the extension is to be .css, then you need to configure the web server to parse .css files through PHP, or use mod_rewrite to point the .css file request to a .php script. Much easier to use a .php extension, at least in testing / if you don't mind the nosey source viewer noticing what you're doing.

My .css coding is NOT clean, by the way; a case of the shoemaker's children having bare feet. For historic reasons, we have a style called "body" and the three if statements in my code all on the same variable could be much neater. I also need to look at adding some cache and store header for the sake of efficiency.