class.cb_css_min.php

<?php
/* This file is part of cbutil.
 * Copyright © 2011-2012 stiftung kulturserver.de ggmbh <github@culturebase.org>
 *
 * cbutil is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * cbutil is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with cbutil.  If not, see <http://www.gnu.org/licenses/>.
 */

/**
 * CSS minifier that is mainly based on regular expressions (since CSS is
 * relatively easy to parse).
 *
 * @author Johannes Wüller <jw@heimat.de>
 */
class CbCssMin {

   /**
    * Stores the unmodified css.
    */
   protected $input = '';

   /**
    * Minifies CSS.
    *
    * @param $css code
    * @return minified code
    */
   public static function minify($css) {
      $minifier = new CbCssMin($css);
      return $minifier->min();
   }

   /**
    * Creates a new minifier.
    *
    * @param $input code
    */
   public function __construct($input) {
      $this->input = $input;
   }

   /**
    * Does the actual minification.
    *
    * @return minified input
    */
   public function min() {
      $output = $this->input;

      // Remove comments.
      $output = preg_replace('/\/\*.*?\*\//s', '', $output);

      // Minimize whitespaces.
      $output = trim($output);
      $output = preg_replace('/\s\s+/', ' ', $output);

      // Remove spaces before and after semicolons, commas, colons, curly
      // braces, parens and the child selector.
      $output = preg_replace('/\s?([;,:\(\)\{\}\>])\s?/', '$1', $output);

      // The space after a media query "and" keyword is required, so put one
      // there to make sure that they will continue to work.
      $output = preg_replace('/\band\(/i', 'and (', $output);

      // Remove semicolons in front of a right curly brace.
      $output = str_replace(';}', '}', $output);

      return $output;
   }

}