CssOptimizer::processCss

protected CssOptimizer::processCss($contents, $optimize = FALSE)

protected function processCss($contents, $optimize = FALSE) {
  // Remove unwanted CSS code that cause issues.
  $contents = $this->clean($contents);

  if ($optimize) {
    // Perform some safe CSS optimizations.
    // Regexp to match comment blocks.
    $comment = '/\*[^*]*\*+(?:[^/*][^*]*\*+)*/';
    // Regexp to match double quoted strings.
    $double_quot = '"[^"\\\\]*(?:\\\\.[^"\\\\]*)*"';
    // Regexp to match single quoted strings.
    $single_quot = "'[^'\\\\]*(?:\\\\.[^'\\\\]*)*'";
    // Strip all comment blocks, but keep double/single quoted strings.
    $contents = preg_replace(
    "<($double_quot|$single_quot)|$comment>Ss", 
    "$1", 
    $contents
    );
    // Remove certain whitespace.
    // There are different conditions for removing leading and trailing
    // whitespace.
    // @see http://php.net/manual/regexp.reference.subpatterns.php
    $contents = preg_replace('<
        # Strip leading and trailing whitespace.
          \s*([@{};,])\s*
        # Strip only leading whitespace from:
        # - Closing parenthesis: Retain "@media (bar) and foo".
        | \s+([\)])
        # Strip only trailing whitespace from:
        # - Opening parenthesis: Retain "@media (bar) and foo".
        # - Colon: Retain :pseudo-selectors.
        | ([\(:])\s+
      >xS', 
    // Only one of the three capturing groups will match, so its reference
    // will contain the wanted value and the references for the
    // two non-matching groups will be replaced with empty strings.
    '$1$2$3', 
    $contents
    );
    // End the file with a new line.
    $contents = trim($contents);
    $contents .= "\n";
  }

  // Replaces @import commands with the actual stylesheet content.
  // This happens recursively but omits external files.
  $contents = preg_replace_callback('/@import\s*(?:url\(\s*)?[\'"]?(?![a-z]+:)(?!\/\/)([^\'"\()]+)[\'"]?\s*\)?\s*;/', array($this, 'loadNestedFile'), $contents);

  return $contents;
}