header('Content-type: text/css');
ob_start("compress");
function compress($buffer) {
  /* remove comments */
  $buffer = preg_replace('!/\*[^*]*\*+([^/][^*]*\*+)*/!', '', $buffer);
  /* remove tabs, spaces, newlines, etc. */
  $buffer = str_replace(array("
", "\r", "\n", "\t", '  ', '    ', '    '), '', $buffer);
  return $buffer;
}

/* your css files */
include('master.css');
include('typography.css');
include('grid.css');
include('print.css');
include('handheld.css');

ob_end_flush();

http://www.phpsnippets.info/compress-css-files-using-php

Paste the code in a file named style.php. Don’t forget to include your css files . Once done, open your HTML document and import style.php as you’ll import a css stylesheet.

Compress CSS files using PHP

css, php

PHP