Minify CSS with PHP

minify-css.php

// Get CSS
$css = get_option( 'css' );
// Remove comments
$buffer = preg_replace('!/\*[^*]*\*+([^/][^*]*\*+)*/!', '', $css);
// Remove space after colons
$buffer = str_replace(': ', ':', $buffer);
// Remove whitespace
$buffer = str_replace(array("\r\n", "\r", "\n", "\t", '  ', '    ', '    '), '', $buffer);
// Display CSS
if ( $buffer ) {
  ?>
  <style type="text/css"><?php echo $buffer; ?></style>
  <?php
}