CSSMin.php | searchcode

/libraries/jyaml/vendor/JsCssChunker/src/lib/compressor/CSSMin.php

https://bitbucket.org/hieblmedia/jyaml
PHP | 804 lines | 462 code | 122 blank | 220 comment | 69 complexity | c14f30dcd0317913418883617d33feb5 MD5 | raw file

<?php
/**
 * JsCssChunker
 *
 * All rights reserved. The JsCssChunker is a PHP Class to minify
 * and compress stylesheet and javascript files.
 * - http://chunker.hieblmedia.net/
 *
 * -----------------------------------------------------------------------------
 *
 * @package    JsCssChunker
 *
 * @author     Reinhard Hiebl <reinhard@hieblmedia.com>
 * @copyright  Copyright (C) 2011 - 2014, HieblMedia (Reinhard Hiebl)
 * @license    http://www.opensource.org/licenses/gpl-3.0.html GNU General Public License, version 3.0 (GPLv3)
 * @link       http://chunker.hieblmedia.net/
 */

/*!
 * cssmin.php rev 91c5ea5
 * Author: Tubal Martin - http://blog.margenn.com/
 * Repo: https://github.com/tubalmartin/YUI-CSS-compressor-PHP-port
 *
 * This is a PHP port of the Javascript port of the CSS minification tool
 * distributed with YUICompressor, itself a port of the cssmin utility by
 * Isaac Schlueter - http://foohack.com/
 * Permission is hereby granted to use the PHP version under the same
 * conditions as the YUICompressor.
 */

/*
 * YUI Compressor
 * http://developer.yahoo.com/yui/compressor/
 * Author: Julien Lecomte - http://www.julienlecomte.net/
 * Copyright (c) 2011 Yahoo! Inc. All rights reserved.
 * The copyrights embodied in the content of this file are licensed
 * by Yahoo! Inc. under the BSD (revised) open source license.
 */

namespace JsCssChunker\Compressor;

/**
 * CSS minifier class
 *
 * @package  JsCssChunker
 * @since    0.0.3
 */
class CSSmin
{
	const NL = '___YUICSSMIN_PRESERVED_NL___';
	const TOKEN = '___YUICSSMIN_PRESERVED_TOKEN_';
	const COMMENT = '___YUICSSMIN_PRESERVE_CANDIDATE_COMMENT_';
	const CLASSCOLON = '___YUICSSMIN_PSEUDOCLASSCOLON___';
	const QUERY_FRACTION = '___YUICSSMIN_QUERY_FRACTION___';

	private $comments;
	private $preserved_tokens;
	private $memory_limit;
	private $max_execution_time;
	private $pcre_backtrack_limit;
	private $pcre_recursion_limit;
	private $raise_php_limits;

	/**
	 * @param bool|int $raise_php_limits
	 * If true, PHP settings will be raised if needed
	 */
	public function __construct($raise_php_limits = TRUE)
	{
		// Set suggested PHP limits
		$this->memory_limit = 128 * 1048576; // 128MB in bytes
		$this->max_execution_time = 60; // 1 min
		$this->pcre_backtrack_limit = 1000 * 1000;
		$this->pcre_recursion_limit =  500 * 1000;

		$this->raise_php_limits = (bool) $raise_php_limits;
	}

	/**
	 * Minify a string of CSS
	 * @param string $css
	 * @param int|bool $linebreak_pos
	 * @return string
	 */
	public function run($css = '', $linebreak_pos = FALSE)
	{
		if (empty($css)) {
			return '';
		}

		if ($this->raise_php_limits) {
			$this->do_raise_php_limits();
		}

		$this->comments = array();
		$this->preserved_tokens = array();

		$start_index = 0;
		$length = strlen($css);

		$css = $this->extract_data_urls($css);

		// collect all comment blocks...
		while (($start_index = $this->index_of($css, '/*', $start_index)) >= 0) {
			$end_index = $this->index_of($css, '*/', $start_index + 2);
			if ($end_index < 0) {
				$end_index = $length;
			}
			$comment_found = $this->str_slice($css, $start_index + 2, $end_index);
			$this->comments[] = $comment_found;
			$comment_preserve_string = self::COMMENT . (count($this->comments) - 1) . '___';
			$css = $this->str_slice($css, 0, $start_index + 2) . $comment_preserve_string . $this->str_slice($css, $end_index);
			// Set correct start_index: Fixes issue #2528130
			$start_index = $end_index + 2 + strlen($comment_preserve_string) - strlen($comment_found);
		}

		// preserve strings so their content doesn't get accidentally minified
		$css = preg_replace_callback('/(?:"(?:[^\\\\"]|\\\\.|\\\\)*")|'."(?:'(?:[^\\\\']|\\\\.|\\\\)*')/S", array($this, 'replace_string'), $css);

		// Let's divide css code in chunks of 5.000 chars aprox.
		// Reason: PHP's PCRE functions like preg_replace have a "backtrack limit"
		// of 100.000 chars by default (php < 5.3.7) so if we're dealing with really
		// long strings and a (sub)pattern matches a number of chars greater than
		// the backtrack limit number (i.e. /(.*)/s) PCRE functions may fail silently
		// returning NULL and $css would be empty.
		$charset = '';
		$charset_regexp = '/(@charset)( [^;]+;)/i';
		$css_chunks = array();
		$css_chunk_length = 5000; // aprox size, not exact
		$start_index = 0;
		$i = $css_chunk_length; // save initial iterations
		$l = strlen($css);


		// if the number of characters is 25000 or less, do not chunk
		if ($l <= $css_chunk_length) {
			$css_chunks[] = $css;
		} else {
			// chunk css code securely
			while ($i < $l) {
				$i += 50; // save iterations
				if ($l - $start_index <= $css_chunk_length || $i >= $l) {
					$css_chunks[] = $this->str_slice($css, $start_index);
					break;
				}
				if ($css[$i - 1] === '}' && $i - $start_index > $css_chunk_length) {
					// If there are two ending curly braces }} separated or not by spaces,
					// join them in the same chunk (i.e. @media blocks)
					$next_chunk = substr($css, $i);
					if (preg_match('/^\s*\}/', $next_chunk)) {
						$i = $i + $this->index_of($next_chunk, '}') + 1;
					}

					$css_chunks[] = $this->str_slice($css, $start_index, $i);
					$start_index = $i;
				}
			}
		}

		// Minify each chunk
		for ($i = 0, $n = count($css_chunks); $i < $n; $i++) {
			$css_chunks[$i] = $this->minify($css_chunks[$i], $linebreak_pos);
			// Keep the first @charset at-rule found
			if (empty($charset) && preg_match($charset_regexp, $css_chunks[$i], $matches)) {
				$charset = strtolower($matches[1]) . $matches[2];
			}
			// Delete all @charset at-rules
			$css_chunks[$i] = preg_replace($charset_regexp, '', $css_chunks[$i]);
		}

		// Update the first chunk and push the charset to the top of the file.
		$css_chunks[0] = $charset . $css_chunks[0];

		return implode('', $css_chunks);
	}

	/**
	 * Sets the memory limit for this script
	 * @param int|string $limit
	 */
	public function set_memory_limit($limit)
	{
		$this->memory_limit = $this->normalize_int($limit);
	}

	/**
	 * Sets the maximum execution time for this script
	 * @param int|string $seconds
	 */
	public function set_max_execution_time($seconds)
	{
		$this->max_execution_time = (int) $seconds;
	}

	/**
	 * Sets the PCRE backtrack limit for this script
	 * @param int $limit
	 */
	public function set_pcre_backtrack_limit($limit)
	{
		$this->pcre_backtrack_limit = (int) $limit;
	}

	/**
	 * Sets the PCRE recursion limit for this script
	 * @param int $limit
	 */
	public function set_pcre_recursion_limit($limit)
	{
		$this->pcre_recursion_limit = (int) $limit;
	}

	/**
	 * Try to configure PHP to use at least the suggested minimum settings
	 */
	private function do_raise_php_limits()
	{
		$php_limits = array(
			'memory_limit' => $this->memory_limit,
			'max_execution_time' => $this->max_execution_time,
			'pcre.backtrack_limit' => $this->pcre_backtrack_limit,
			'pcre.recursion_limit' =>  $this->pcre_recursion_limit
		);

		// If current settings are higher respect them.
		foreach ($php_limits as $name => $suggested) {
			$current = $this->normalize_int(ini_get($name));
			// memory_limit exception: allow -1 for "no memory limit".
			if ($current > -1 && ($suggested == -1 || $current < $suggested)) {
				ini_set($name, $suggested);
			}
		}
	}

	/**
	 * Does bulk of the minification
	 * @param string $css
	 * @param int|bool $linebreak_pos
	 * @return string
	 */
	private function minify($css, $linebreak_pos)
	{
		// strings are safe, now wrestle the comments
		for ($i = 0, $max = count($this->comments); $i < $max; $i++) {

			$token = $this->comments[$i];
			$placeholder = '/' . self::COMMENT . $i . '___/';

			// ! in the first position of the comment means preserve
			// so push to the preserved tokens keeping the !
			if (substr($token, 0, 1) === '!') {
				$this->preserved_tokens[] = $token;
				$token_tring = self::TOKEN . (count($this->preserved_tokens) - 1) . '___';
				$css = preg_replace($placeholder, $token_tring, $css, 1);
				// Preserve new lines for /*! important comments
				$css = preg_replace('/\s*[\n\r\f]+\s*(\/\*'. $token_tring .')/S', self::NL.'$1', $css);
				$css = preg_replace('/('. $token_tring .'\*\/)\s*[\n\r\f]+\s*/', '$1'.self::NL, $css);
				continue;
			}

			// \ in the last position looks like hack for Mac/IE5
			// shorten that to /*\*/ and the next one to /**/
			if (substr($token, (strlen($token) - 1), 1) === '\\') {
				$this->preserved_tokens[] = '\\';
				$css = preg_replace($placeholder,  self::TOKEN . (count($this->preserved_tokens) - 1) . '___', $css, 1);
				$i = $i + 1; // attn: advancing the loop
				$this->preserved_tokens[] = '';
				$css = preg_replace('/' . self::COMMENT . $i . '___/',  self::TOKEN . (count($this->preserved_tokens) - 1) . '___', $css, 1);
				continue;
			}

			// keep empty comments after child selectors (IE7 hack)
			// e.g. html >/**/ body
			if (strlen($token) === 0) {
				$start_index = $this->index_of($css, $this->str_slice($placeholder, 1, -1));
				if ($start_index > 2) {
					if (substr($css, $start_index - 3, 1) === '>') {
						$this->preserved_tokens[] = '';
						$css = preg_replace($placeholder,  self::TOKEN . (count($this->preserved_tokens) - 1) . '___', $css, 1);
					}
				}
			}

			// in all other cases kill the comment
			$css = preg_replace('/\/\*' . $this->str_slice($placeholder, 1, -1) . '\*\//', '', $css, 1);
		}


		// Normalize all whitespace strings to single spaces. Easier to work with that way.
		$css = preg_replace('/\s+/', ' ', $css);

		// Fix IE7 issue on matrix filters which browser accept whitespaces between Matrix parameters
		$css = preg_replace_callback('/\s*filter\:\s*progid:DXImageTransform\.Microsoft\.Matrix\(([^\)]+)\)/', array($this, 'preserve_old_IE_specific_matrix_definition'), $css);

		// Shorten & preserve calculations calc(...) since spaces are important
		$css = preg_replace_callback('/calc(\(((?:[^\(\)]+|(?1))*)\))/i', array($this, 'replace_calc'), $css);

		// Replace positive sign from numbers preceded by : or a white-space before the leading space is removed
		// +1.2em to 1.2em, +.8px to .8px, +2% to 2%
		$css = preg_replace('/((?<!\\\\)\:|\s)\+(\.?\d+)/S', '$1$2', $css);

		// Remove leading zeros from integer and float numbers preceded by : or a white-space
		// 000.6 to .6, -0.8 to -.8, 0050 to 50, -01.05 to -1.05
		$css = preg_replace('/((?<!\\\\)\:|\s)(\-?)0+(\.?\d+)/S', '$1$2$3', $css);

		// Remove trailing zeros from float numbers preceded by : or a white-space
		// -6.0100em to -6.01em, .0100 to .01, 1.200px to 1.2px
		$css = preg_replace('/((?<!\\\\)\:|\s)(\-?)(\d?\.\d+?)0+([^\d])/S', '$1$2$3$4', $css);

		// Remove trailing .0 -> -9.0 to -9
		$css = preg_replace('/((?<!\\\\)\:|\s)(\-?\d+)\.0([^\d])/S', '$1$2$3', $css);

		// Replace 0 length numbers with 0
		$css = preg_replace('/((?<!\\\\)\:|\s)\-?\.?0+([^\d])/S', '${1}0$2', $css);

		// Remove the spaces before the things that should not have spaces before them.
		// But, be careful not to turn "p :link {...}" into "p:link{...}"
		// Swap out any pseudo-class colons with the token, and then swap back.
		$css = preg_replace_callback('/(?:^|\})(?:(?:[^\{\:])+\:)+(?:[^\{]*\{)/', array($this, 'replace_colon'), $css);

		// Remove spaces before the things that should not have spaces before them.
		$css = preg_replace('/\s+([\!\{\}\;\:\>\+\(\)\]\~\=,])/', '$1', $css);

		// Restore spaces for !important
		$css = preg_replace('/\!important/i', ' !important', $css);

		// bring back the colon
		$css = preg_replace('/' . self::CLASSCOLON . '/', ':', $css);

		// retain space for special IE6 cases
		$css = preg_replace_callback('/\:first\-(line|letter)(\{|,)/i', array($this, 'lowercase_pseudo_first'), $css);

		// no space after the end of a preserved comment
		$css = preg_replace('/\*\/ /', '*/', $css);

		// lowercase some popular @directives
		$css = preg_replace_callback('/@(font-face|import|(?:-(?:atsc|khtml|moz|ms|o|wap|webkit)-)?keyframe|media|page|namespace)/i', array($this, 'lowercase_directives'), $css);

		// lowercase some more common pseudo-elements
		$css = preg_replace_callback('/:(active|after|before|checked|disabled|empty|enabled|first-(?:child|of-type)|focus|hover|last-(?:child|of-type)|link|only-(?:child|of-type)|root|:selection|target|visited)/i', array($this, 'lowercase_pseudo_elements'), $css);

		// lowercase some more common functions
		$css = preg_replace_callback('/:(lang|not|nth-child|nth-last-child|nth-last-of-type|nth-of-type|(?:-(?:moz|webkit)-)?any)\(/i', array($this, 'lowercase_common_functions'), $css);

		// lower case some common function that can be values
		// NOTE: rgb() isn't useful as we replace with #hex later, as well as and() is already done for us
		$css = preg_replace_callback('/([:,\( ]\s*)(attr|color-stop|from|rgba|to|url|(?:-(?:atsc|khtml|moz|ms|o|wap|webkit)-)?(?:calc|max|min|(?:repeating-)?(?:linear|radial)-gradient)|-webkit-gradient)/iS', array($this, 'lowercase_common_functions_values'), $css);

		// Put the space back in some cases, to support stuff like
		// @media screen and (-webkit-min-device-pixel-ratio:0){
		$css = preg_replace('/\band\(/i', 'and (', $css);

		// Put the space back in for @support tag
		// @supports (display: flex) and  @supports not (display: flex)
		$css = preg_replace('/\b(supports|not)\(/i', '$1 (', $css);

		// Remove the spaces after the things that should not have spaces after them.
		$css = preg_replace('/([\!\{\}\:;\>\+\(\[\~\=,])\s+/S', '$1', $css);

		// remove unnecessary semicolons
		$css = preg_replace('/;+\}/', '}', $css);

		// Fix for issue: #2528146
		// Restore semicolon if the last property is prefixed with a `*` (lte IE7 hack)
		// to avoid issues on Symbian S60 3.x browsers.
		$css = preg_replace('/(\*[a-z0-9\-]+\s*\:[^;\}]+)(\})/', '$1;$2', $css);

		// Replace 0 length units 0(px,em,%) with 0.
		$css = preg_replace('/(^|[^0-9])(?:0?\.)?0(?:em|ex|ch|rem|vw|vh|vm|vmin|cm|mm|in|px|pt|pc|%|deg|g?rad|m?s|k?hz)/iS', '${1}0', $css);

		// 0% step in a keyframe? restore the % unit
		$css = preg_replace_callback('/(@[a-z\-]*?keyframes[^\{]*?\{)(.*?\}\s*\})/iS', array($this, 'replace_keyframe_zero'), $css);

		// Replace 0 0; or 0 0 0; or 0 0 0 0; with 0.
		$css = preg_replace('/\:0(?: 0){1,3}(;|\}| \!)/', ':0$1', $css);

		// Fix for issue: #2528142
		// Replace text-shadow:0; with text-shadow:0 0 0;
		$css = preg_replace('/(text-shadow\:0)(;|\}| \!)/i', '$1 0 0$2', $css);

		// Replace background-position:0; with background-position:0 0;
		// same for transform-origin
		// Changing -webkit-mask-position: 0 0 to just a single 0 will result in the second parameter defaulting to 50% (center)
		$css = preg_replace('/(background\-position|webkit-mask-position|(?:webkit|moz|o|ms|)\-?transform\-origin)\:0(;|\}| \!)/iS', '$1:0 0$2', $css);

		// Shorten colors from rgb(51,102,153) to #336699, rgb(100%,0%,0%) to #ff0000 (sRGB color space)
		// Shorten colors from hsl(0, 100%, 50%) to #ff0000 (sRGB color space)
		// This makes it more likely that it'll get further compressed in the next step.
		$css = preg_replace_callback('/rgb\s*\(\s*([0-9,\s\-\.\%]+)\s*\)(.{1})/i', array($this, 'rgb_to_hex'), $css);
		$css = preg_replace_callback('/hsl\s*\(\s*([0-9,\s\-\.\%]+)\s*\)(.{1})/i', array($this, 'hsl_to_hex'), $css);

		// Shorten colors from #AABBCC to #ABC or short color name.
		$css = $this->compress_hex_colors($css);

		// border: none to border:0, outline: none to outline:0
		$css = preg_replace('/(border\-?(?:top|right|bottom|left|)|outline)\:none(;|\}| \!)/iS', '$1:0$2', $css);

		// shorter opacity IE filter
		$css = preg_replace('/progid\:DXImageTransform\.Microsoft\.Alpha\(Opacity\=/i', 'alpha(opacity=', $css);

		// Find a fraction that is used for Opera's -o-device-pixel-ratio query
		// Add token to add the "\" back in later
		$css = preg_replace('/\(([a-z\-]+):([0-9]+)\/([0-9]+)\)/i', '($1:$2'. self::QUERY_FRACTION .'$3)', $css);

		// Remove empty rules.
		$css = preg_replace('/[^\};\{\/]+\{\}/S', '', $css);

		// Add "/" back to fix Opera -o-device-pixel-ratio query
		$css = preg_replace('/'. self::QUERY_FRACTION .'/', '/', $css);

		// Replace multiple semi-colons in a row by a single one
		// See SF bug #1980989
		$css = preg_replace('/;;+/', ';', $css);

		// Restore new lines for /*! important comments
		$css = preg_replace('/'. self::NL .'/', "\n", $css);

		// Lowercase all uppercase properties
		$css = preg_replace_callback('/(\{|\;)([A-Z\-]+)(\:)/', array($this, 'lowercase_properties'), $css);

		// Some source control tools don't like it when files containing lines longer
		// than, say 8000 characters, are checked in. The linebreak option is used in
		// that case to split long lines after a specific column.
		if ($linebreak_pos !== FALSE && (int) $linebreak_pos >= 0) {
			$linebreak_pos = (int) $linebreak_pos;
			$start_index = $i = 0;
			while ($i < strlen($css)) {
				$i++;
				if ($css[$i - 1] === '}' && $i - $start_index > $linebreak_pos) {
					$css = $this->str_slice($css, 0, $i) . "\n" . $this->str_slice($css, $i);
					$start_index = $i;
				}
			}
		}

		// restore preserved comments and strings in reverse order
		for ($i = count($this->preserved_tokens) - 1; $i >= 0; $i--) {
			$css = preg_replace('/' . self::TOKEN . $i . '___/', $this->preserved_tokens[$i], $css, 1);
		}

		// Trim the final string (for any leading or trailing white spaces)
		return trim($css);
	}

	/**
	 * Utility method to replace all data urls with tokens before we start
	 * compressing, to avoid performance issues running some of the subsequent
	 * regexes against large strings chunks.
	 *
	 * @param string $css
	 * @return string
	 */
	private function extract_data_urls($css)
	{
		// Leave data urls alone to increase parse performance.
		$max_index = strlen($css) - 1;
		$append_index = $index = $last_index = $offset = 0;
		$sb = array();
		$pattern = '/url\(\s*(["\']?)data\:/i';

		// Since we need to account for non-base64 data urls, we need to handle
		// ' and ) being part of the data string. Hence switching to indexOf,
		// to determine whether or not we have matching string terminators and
		// handling sb appends directly, instead of using matcher.append* methods.

		while (preg_match($pattern, $css, $m, 0, $offset)) {
			$index = $this->index_of($css, $m[0], $offset);
			$last_index = $index + strlen($m[0]);
			$start_index = $index + 4; // "url(".length()
			$end_index = $last_index - 1;
			$terminator = $m[1]; // ', " or empty (not quoted)
			$found_terminator = FALSE;

			if (strlen($terminator) === 0) {
				$terminator = ')';
			}

			while ($found_terminator === FALSE && $end_index+1 <= $max_index) {
				$end_index = $this->index_of($css, $terminator, $end_index + 1);

				// endIndex == 0 doesn't really apply here
				if ($end_index > 0 && substr($css, $end_index - 1, 1) !== '\\') {
					$found_terminator = TRUE;
					if (')' != $terminator) {
						$end_index = $this->index_of($css, ')', $end_index);
					}
				}
			}

			// Enough searching, start moving stuff over to the buffer
			$sb[] = $this->str_slice($css, $append_index, $index);

			if ($found_terminator) {
				$token = $this->str_slice($css, $start_index, $end_index);
				$token = preg_replace('/\s+/', '', $token);
				$this->preserved_tokens[] = $token;

				$preserver = 'url(' . self::TOKEN . (count($this->preserved_tokens) - 1) . '___)';
				$sb[] = $preserver;

				$append_index = $end_index + 1;
			} else {
				// No end terminator found, re-add the whole match. Should we throw/warn here?
				$sb[] = $this->str_slice($css, $index, $last_index);
				$append_index = $last_index;
			}

			$offset = $last_index;
		}

		$sb[] = $this->str_slice($css, $append_index);

		return implode('', $sb);
	}

	/**
	 * Utility method to compress hex color values of the form #AABBCC to #ABC or short color name.
	 *
	 * DOES NOT compress CSS ID selectors which match the above pattern (which would break things).
	 * e.g. #AddressForm { ... }
	 *
	 * DOES NOT compress IE filters, which have hex color values (which would break things).
	 * e.g. filter: chroma(color="#FFFFFF");
	 *
	 * DOES NOT compress invalid hex values.
	 * e.g. background-color: #aabbccdd
	 *
	 * @param string $css
	 * @return string
	 */
	private function compress_hex_colors($css)
	{
		// Look for hex colors inside { ... } (to avoid IDs) and which don't have a =, or a " in front of them (to avoid filters)
		$pattern = '/(\=\s*?["\']?)?#([0-9a-f])([0-9a-f])([0-9a-f])([0-9a-f])([0-9a-f])([0-9a-f])(\}|[^0-9a-f{][^{]*?\})/iS';
		$_index = $index = $last_index = $offset = 0;
		$sb = array();
		// See: http://ajaxmin.codeplex.com/wikipage?title=CSS%20Colors
		$short_safe = array(
			'#808080' => 'gray',
			'#008000' => 'green',
			'#800000' => 'maroon',
			'#000080' => 'navy',
			'#808000' => 'olive',
			'#ffa500' => 'orange',
			'#800080' => 'purple',
			'#c0c0c0' => 'silver',
			'#008080' => 'teal',
			'#f00' => 'red'
		);

		while (preg_match($pattern, $css, $m, 0, $offset)) {
			$index = $this->index_of($css, $m[0], $offset);
			$last_index = $index + strlen($m[0]);
			$is_filter = $m[1] !== null && $m[1] !== '';

			$sb[] = $this->str_slice($css, $_index, $index);

			if ($is_filter) {
				// Restore, maintain case, otherwise filter will break
				$sb[] = $m[1] . '#' . $m[2] . $m[3] . $m[4] . $m[5] . $m[6] . $m[7];
			} else {
				if (strtolower($m[2]) == strtolower($m[3]) &&
				    strtolower($m[4]) == strtolower($m[5]) &&
				    strtolower($m[6]) == strtolower($m[7])) {
					// Compress.
					$hex = '#' . strtolower($m[3] . $m[5] . $m[7]);
				} else {
					// Non compressible color, restore but lower case.
					$hex = '#' . strtolower($m[2] . $m[3] . $m[4] . $m[5] . $m[6] . $m[7]);
				}
				// replace Hex colors to short safe color names
				$sb[] = array_key_exists($hex, $short_safe) ? $short_safe[$hex] : $hex;
			}

			$_index = $offset = $last_index - strlen($m[8]);
		}

		$sb[] = $this->str_slice($css, $_index);

		return implode('', $sb);
	}

	/* CALLBACKS
	 * ---------------------------------------------------------------------------------------------
	 */

	private function replace_string($matches)
	{
		$match = $matches[0];
		$quote = substr($match, 0, 1);
		// Must use addcslashes in PHP to avoid parsing of backslashes
		$match = addcslashes($this->str_slice($match, 1, -1), '\\');

		// maybe the string contains a comment-like substring?
		// one, maybe more? put'em back then
		if (($pos = $this->index_of($match, self::COMMENT)) >= 0) {
			for ($i = 0, $max = count($this->comments); $i < $max; $i++) {
				$match = preg_replace('/' . self::COMMENT . $i . '___/', $this->comments[$i], $match, 1);
			}
		}

		// minify alpha opacity in filter strings
		$match = preg_replace('/progid\:DXImageTransform\.Microsoft\.Alpha\(Opacity\=/i', 'alpha(opacity=', $match);

		$this->preserved_tokens[] = $match;
		return $quote . self::TOKEN . (count($this->preserved_tokens) - 1) . '___' . $quote;
	}

	private function replace_colon($matches)
	{
		return preg_replace('/\:/', self::CLASSCOLON, $matches[0]);
	}

	private function replace_calc($matches)
	{
		$this->preserved_tokens[] = trim(preg_replace('/\s*([\*\/\(\),])\s*/', '$1', $matches[2]));
		return 'calc('. self::TOKEN . (count($this->preserved_tokens) - 1) . '___' . ')';
	}

	private function preserve_old_IE_specific_matrix_definition($matches)
	{
		$this->preserved_tokens[] = $matches[1];
		return 'filter:progid:DXImageTransform.Microsoft.Matrix(' . self::TOKEN . (count($this->preserved_tokens) - 1) . '___' . ')';
	}

	private function replace_keyframe_zero($matches)
	{
		return $matches[1] . preg_replace('/0\s*,/', '0%,', preg_replace('/\s*0\s*\{/', '0%{', $matches[2]));
	}

	private function rgb_to_hex($matches)
	{
		// Support for percentage values rgb(100%, 0%, 45%);
		if ($this->index_of($matches[1], '%') >= 0){
			$rgbcolors = explode(',', str_replace('%', '', $matches[1]));
			for ($i = 0; $i < count($rgbcolors); $i++) {
				$rgbcolors[$i] = $this->round_number(floatval($rgbcolors[$i]) * 2.55);
			}
		} else {
			$rgbcolors = explode(',', $matches[1]);
		}

		// Values outside the sRGB color space should be clipped (0-255)
		for ($i = 0; $i < count($rgbcolors); $i++) {
			$rgbcolors[$i] = $this->clamp_number(intval($rgbcolors[$i], 10), 0, 255);
			$rgbcolors[$i] = sprintf("%02x", $rgbcolors[$i]);
		}

		// Fix for issue #2528093
		if (!preg_match('/[\s\,\);\}]/', $matches[2])){
			$matches[2] = ' ' . $matches[2];
		}

		return '#' . implode('', $rgbcolors) . $matches[2];
	}

	private function hsl_to_hex($matches)
	{
		$values = explode(',', str_replace('%', '', $matches[1]));
		$h = floatval($values[0]);
		$s = floatval($values[1]);
		$l = floatval($values[2]);

		// Wrap and clamp, then fraction!
		$h = ((($h % 360) + 360) % 360) / 360;
		$s = $this->clamp_number($s, 0, 100) / 100;
		$l = $this->clamp_number($l, 0, 100) / 100;

		if ($s == 0) {
			$r = $g = $b = $this->round_number(255 * $l);
		} else {
			$v2 = $l < 0.5 ? $l * (1 + $s) : ($l + $s) - ($s * $l);
			$v1 = (2 * $l) - $v2;
			$r = $this->round_number(255 * $this->hue_to_rgb($v1, $v2, $h + (1/3)));
			$g = $this->round_number(255 * $this->hue_to_rgb($v1, $v2, $h));
			$b = $this->round_number(255 * $this->hue_to_rgb($v1, $v2, $h - (1/3)));
		}

		return $this->rgb_to_hex(array('', $r.','.$g.','.$b, $matches[2]));
	}

	private function lowercase_pseudo_first($matches)
	{
		return ':first-'. strtolower($matches[1]) .' '. $matches[2];
	}

	private function lowercase_directives($matches)
	{
		return '@'. strtolower($matches[1]);
	}

	private function lowercase_pseudo_elements($matches)
	{
		return ':'. strtolower($matches[1]);
	}

	private function lowercase_common_functions($matches)
	{
		return ':'. strtolower($matches[1]) .'(';
	}

	private function lowercase_common_functions_values($matches)
	{
		return $matches[1] . strtolower($matches[2]);
	}

	private function lowercase_properties($matches)
	{
		return $matches[1].strtolower($matches[2]).$matches[3];
	}

	/* HELPERS
	 * ---------------------------------------------------------------------------------------------
	 */

	private function hue_to_rgb($v1, $v2, $vh)
	{
		$vh = $vh < 0 ? $vh + 1 : ($vh > 1 ? $vh - 1 : $vh);
		if ($vh * 6 < 1) return $v1 + ($v2 - $v1) * 6 * $vh;
		if ($vh * 2 < 1) return $v2;
		if ($vh * 3 < 2) return $v1 + ($v2 - $v1) * ((2/3) - $vh) * 6;
		return $v1;
	}

	private function round_number($n)
	{
		return intval(floor(floatval($n) + 0.5), 10);
	}

	private function clamp_number($n, $min, $max)
	{
		return min(max($n, $min), $max);
	}

	/**
	 * PHP port of Javascript's "indexOf" function for strings only
	 * Author: Tubal Martin http://blog.margenn.com
	 *
	 * @param string $haystack
	 * @param string $needle
	 * @param int    $offset index (optional)
	 * @return int
	 */
	private function index_of($haystack, $needle, $offset = 0)
	{
		$index = strpos($haystack, $needle, $offset);

		return ($index !== FALSE) ? $index : -1;
	}

	/**
	 * PHP port of Javascript's "slice" function for strings only
	 * Author: Tubal Martin http://blog.margenn.com
	 * Tests: http://margenn.com/tubal/str_slice/
	 *
	 * @param string   $str
	 * @param int      $start index
	 * @param int|bool $end index (optional)
	 * @return string
	 */
	private function str_slice($str, $start = 0, $end = FALSE)
	{
		if ($end !== FALSE && ($start < 0 || $end <= 0)) {
			$max = strlen($str);

			if ($start < 0) {
				if (($start = $max + $start) < 0) {
					return '';
				}
			}

			if ($end < 0) {
				if (($end = $max + $end) < 0) {
					return '';
				}
			}

			if ($end <= $start) {
				return '';
			}
		}

		$slice = ($end === FALSE) ? substr($str, $start) : substr($str, $start, $end - $start);
		return ($slice === FALSE) ? '' : $slice;
	}

	/**
	 * Convert strings like "64M" or "30" to int values
	 * @param mixed $size
	 * @return int
	 */
	private function normalize_int($size)
	{
		if (is_string($size)) {
			switch (substr($size, -1)) {
				case 'M': case 'm': return $size * 1048576;
				case 'K': case 'k': return $size * 1024;
				case 'G': case 'g': return $size * 1073741824;
			}
		}

		return (int) $size;
	}
}