how to chage css using php code example

Example: change css in php

Rename your style.css file to style.php, then add the following to the top of the file:

<?php header("Content-type: text/css"); ?>
This line tells the browser that the file is CSS instead of HTML. 
In your HTML files, change the stylesheet references from style.css to style.php. For example:

<link rel="stylesheet" type="text/css"
 media="screen" href="style.php">