I'm assuming you want one file to process different CSS based on different parameters.
I have a better answer, and as a benefit to this answer, you can have pretty urls instead of requiring a client browser to call actual CSS files.
I'm gonna assume a standard LAMP setup (Linux, Apache, MySQL, and PHP) is done on the remote computer. First, ask the server administrator to enable the Mod_rewrite module. Then create a new text file using windows notepad or similar, and type in the following contents:
RewriteEngine On
RewriteRule ^css/version/(.+)$ css.php?ver=$1 [L]
Save the file as .htaccess and then upload it to your css folder (or the folder where front.css is expected to go).
Next, create a new text file in notepad (yes, again.) and then type in the following:
<?php
error_reporting(7); //suppress most errors including undefined errors
$version=$_GET["ver"];
$tm=60*60*24*8; // 8 days in future.
header('Expires: '.gmdate('D, d M Y H:i:s',time() +$tm).' GMT',true);
header('Cache-control: max-age='.$tm,true);
header('Content-type: text/css',true);
switch ($version){
case "4.1":
?>
.style4point1body {background-color: blue;}
.style4point1button {color: red;}
.style4point1header {font-size: 200%;}
<?php
break;
case "2.0":
?>
.style2point0body {background-color: red;}
.style2point0button {color: green;}
.style2point0header {font-size: 300%;}
<?php
break;
default:
?>
.undefinedstylebody {background-color: black;}
.undefinedstylebutton {color: yellow;}
.undefinedstyleheader {font-size: 50%;}
<?php
break;
}
?>
Save it as css.php and put it in the same folder where you put the newly created .htaccess file.
Now you can access these urls (where ... is what you normally type in before css/front.css?ver=4.1):
...css/version/4.1
...css/version/2.0
...css/version/<anything you want>
Now this is where it gets interesting. If you access the first URL, the following code will load:
.style4point1body {background-color: blue;}
.style4point1button {color: red;}
.style4point1header {font-size: 200%;}
And if you access the second URL, the following code will load:
.style2point0body {background-color: red;}
.style2point0button {color: green;}
.style2point0header {font-size: 300%;}
And if you access the third URL or any other URL that starts with .../css/version/ then you'll get this code:
.undefinedstylebody {background-color: black;}
.undefinedstylebutton {color: yellow;}
.undefinedstyleheader {font-size: 50%;}
I made the code so the page expires 8 days later from the current time, but if you need to adjust the days, change the 8 in the line starting with $tm.