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See Release Notes
Long Term Support Release

  • Bug fixes for general core bugs in 4.1.x will end 13 November 2023 (12 months).
  • Bug fixes for security issues in 4.1.x will end 10 November 2025 (36 months).
  • PHP version: minimum PHP 7.4.0 Note: minimum PHP version has increased since Moodle 4.0. PHP 8.0.x is supported too.

Differences Between: [Versions 310 and 401] [Versions 311 and 401] [Versions 39 and 401] [Versions 400 and 401] [Versions 401 and 402] [Versions 401 and 403]

   1  <?php
   2  /**
   3   * CSS Minifier
   4   *
   5   * Please report bugs on https://github.com/matthiasmullie/minify/issues
   6   *
   7   * @author Matthias Mullie <minify@mullie.eu>
   8   * @copyright Copyright (c) 2012, Matthias Mullie. All rights reserved
   9   * @license MIT License
  10   */
  11  
  12  namespace MatthiasMullie\Minify;
  13  
  14  use MatthiasMullie\Minify\Exceptions\FileImportException;
  15  use MatthiasMullie\PathConverter\ConverterInterface;
  16  use MatthiasMullie\PathConverter\Converter;
  17  
  18  /**
  19   * CSS minifier
  20   *
  21   * Please report bugs on https://github.com/matthiasmullie/minify/issues
  22   *
  23   * @package Minify
  24   * @author Matthias Mullie <minify@mullie.eu>
  25   * @author Tijs Verkoyen <minify@verkoyen.eu>
  26   * @copyright Copyright (c) 2012, Matthias Mullie. All rights reserved
  27   * @license MIT License
  28   */
  29  class CSS extends Minify
  30  {
  31      /**
  32       * @var int maximum inport size in kB
  33       */
  34      protected $maxImportSize = 5;
  35  
  36      /**
  37       * @var string[] valid import extensions
  38       */
  39      protected $importExtensions = array(
  40          'gif' => 'data:image/gif',
  41          'png' => 'data:image/png',
  42          'jpe' => 'data:image/jpeg',
  43          'jpg' => 'data:image/jpeg',
  44          'jpeg' => 'data:image/jpeg',
  45          'svg' => 'data:image/svg+xml',
  46          'woff' => 'data:application/x-font-woff',
  47          'woff2' => 'data:application/x-font-woff2',
  48          'avif' => 'data:image/avif',
  49          'apng' => 'data:image/apng',
  50          'webp' => 'data:image/webp',
  51          'tif' => 'image/tiff',
  52          'tiff' => 'image/tiff',
  53          'xbm' => 'image/x-xbitmap',
  54      );
  55  
  56      /**
  57       * Set the maximum size if files to be imported.
  58       *
  59       * Files larger than this size (in kB) will not be imported into the CSS.
  60       * Importing files into the CSS as data-uri will save you some connections,
  61       * but we should only import relatively small decorative images so that our
  62       * CSS file doesn't get too bulky.
  63       *
  64       * @param int $size Size in kB
  65       */
  66      public function setMaxImportSize($size)
  67      {
  68          $this->maxImportSize = $size;
  69      }
  70  
  71      /**
  72       * Set the type of extensions to be imported into the CSS (to save network
  73       * connections).
  74       * Keys of the array should be the file extensions & respective values
  75       * should be the data type.
  76       *
  77       * @param string[] $extensions Array of file extensions
  78       */
  79      public function setImportExtensions(array $extensions)
  80      {
  81          $this->importExtensions = $extensions;
  82      }
  83  
  84      /**
  85       * Move any import statements to the top.
  86       *
  87       * @param string $content Nearly finished CSS content
  88       *
  89       * @return string
  90       */
  91      protected function moveImportsToTop($content)
  92      {
  93          if (preg_match_all('/(;?)(@import (?<url>url\()?(?P<quotes>["\']?).+?(?P=quotes)(?(url)\)));?/', $content, $matches)) {
  94              // remove from content
  95              foreach ($matches[0] as $import) {
  96                  $content = str_replace($import, '', $content);
  97              }
  98  
  99              // add to top
 100              $content = implode(';', $matches[2]).';'.trim($content, ';');
 101          }
 102  
 103          return $content;
 104      }
 105  
 106      /**
 107       * Combine CSS from import statements.
 108       *
 109       * @import's will be loaded and their content merged into the original file,
 110       * to save HTTP requests.
 111       *
 112       * @param string   $source  The file to combine imports for
 113       * @param string   $content The CSS content to combine imports for
 114       * @param string[] $parents Parent paths, for circular reference checks
 115       *
 116       * @return string
 117       *
 118       * @throws FileImportException
 119       */
 120      protected function combineImports($source, $content, $parents)
 121      {
 122          $importRegexes = array(
 123              // @import url(xxx)
 124              '/
 125              # import statement
 126              @import
 127  
 128              # whitespace
 129              \s+
 130  
 131                  # open url()
 132                  url\(
 133  
 134                      # (optional) open path enclosure
 135                      (?P<quotes>["\']?)
 136  
 137                          # fetch path
 138                          (?P<path>.+?)
 139  
 140                      # (optional) close path enclosure
 141                      (?P=quotes)
 142  
 143                  # close url()
 144                  \)
 145  
 146                  # (optional) trailing whitespace
 147                  \s*
 148  
 149                  # (optional) media statement(s)
 150                  (?P<media>[^;]*)
 151  
 152                  # (optional) trailing whitespace
 153                  \s*
 154  
 155              # (optional) closing semi-colon
 156              ;?
 157  
 158              /ix',
 159  
 160              // @import 'xxx'
 161              '/
 162  
 163              # import statement
 164              @import
 165  
 166              # whitespace
 167              \s+
 168  
 169                  # open path enclosure
 170                  (?P<quotes>["\'])
 171  
 172                      # fetch path
 173                      (?P<path>.+?)
 174  
 175                  # close path enclosure
 176                  (?P=quotes)
 177  
 178                  # (optional) trailing whitespace
 179                  \s*
 180  
 181                  # (optional) media statement(s)
 182                  (?P<media>[^;]*)
 183  
 184                  # (optional) trailing whitespace
 185                  \s*
 186  
 187              # (optional) closing semi-colon
 188              ;?
 189  
 190              /ix',
 191          );
 192  
 193          // find all relative imports in css
 194          $matches = array();
 195          foreach ($importRegexes as $importRegex) {
 196              if (preg_match_all($importRegex, $content, $regexMatches, PREG_SET_ORDER)) {
 197                  $matches = array_merge($matches, $regexMatches);
 198              }
 199          }
 200  
 201          $search = array();
 202          $replace = array();
 203  
 204          // loop the matches
 205          foreach ($matches as $match) {
 206              // get the path for the file that will be imported
 207              $importPath = dirname($source).'/'.$match['path'];
 208  
 209              // only replace the import with the content if we can grab the
 210              // content of the file
 211              if (!$this->canImportByPath($match['path']) || !$this->canImportFile($importPath)) {
 212                  continue;
 213              }
 214  
 215              // check if current file was not imported previously in the same
 216              // import chain.
 217              if (in_array($importPath, $parents)) {
 218                  throw new FileImportException('Failed to import file "'.$importPath.'": circular reference detected.');
 219              }
 220  
 221              // grab referenced file & minify it (which may include importing
 222              // yet other @import statements recursively)
 223              $minifier = new self($importPath);
 224              $minifier->setMaxImportSize($this->maxImportSize);
 225              $minifier->setImportExtensions($this->importExtensions);
 226              $importContent = $minifier->execute($source, $parents);
 227  
 228              // check if this is only valid for certain media
 229              if (!empty($match['media'])) {
 230                  $importContent = '@media '.$match['media'].'{'.$importContent.'}';
 231              }
 232  
 233              // add to replacement array
 234              $search[] = $match[0];
 235              $replace[] = $importContent;
 236          }
 237  
 238          // replace the import statements
 239          return str_replace($search, $replace, $content);
 240      }
 241  
 242      /**
 243       * Import files into the CSS, base64-ized.
 244       *
 245       * @url(image.jpg) images will be loaded and their content merged into the
 246       * original file, to save HTTP requests.
 247       *
 248       * @param string $source  The file to import files for
 249       * @param string $content The CSS content to import files for
 250       *
 251       * @return string
 252       */
 253      protected function importFiles($source, $content)
 254      {
 255          $regex = '/url\((["\']?)(.+?)\\1\)/i';
 256          if ($this->importExtensions && preg_match_all($regex, $content, $matches, PREG_SET_ORDER)) {
 257              $search = array();
 258              $replace = array();
 259  
 260              // loop the matches
 261              foreach ($matches as $match) {
 262                  $extension = substr(strrchr($match[2], '.'), 1);
 263                  if ($extension && !array_key_exists($extension, $this->importExtensions)) {
 264                      continue;
 265                  }
 266  
 267                  // get the path for the file that will be imported
 268                  $path = $match[2];
 269                  $path = dirname($source).'/'.$path;
 270  
 271                  // only replace the import with the content if we're able to get
 272                  // the content of the file, and it's relatively small
 273                  if ($this->canImportFile($path) && $this->canImportBySize($path)) {
 274                      // grab content && base64-ize
 275                      $importContent = $this->load($path);
 276                      $importContent = base64_encode($importContent);
 277  
 278                      // build replacement
 279                      $search[] = $match[0];
 280                      $replace[] = 'url('.$this->importExtensions[$extension].';base64,'.$importContent.')';
 281                  }
 282              }
 283  
 284              // replace the import statements
 285              $content = str_replace($search, $replace, $content);
 286          }
 287  
 288          return $content;
 289      }
 290  
 291      /**
 292       * Minify the data.
 293       * Perform CSS optimizations.
 294       *
 295       * @param string[optional] $path    Path to write the data to
 296       * @param string[]         $parents Parent paths, for circular reference checks
 297       *
 298       * @return string The minified data
 299       */
 300      public function execute($path = null, $parents = array())
 301      {
 302          $content = '';
 303  
 304          // loop CSS data (raw data and files)
 305          foreach ($this->data as $source => $css) {
 306              /*
 307               * Let's first take out strings & comments, since we can't just
 308               * remove whitespace anywhere. If whitespace occurs inside a string,
 309               * we should leave it alone. E.g.:
 310               * p { content: "a   test" }
 311               */
 312              $this->extractStrings();
 313              $this->stripComments();
 314              $this->extractMath();
 315              $this->extractCustomProperties();
 316              $css = $this->replace($css);
 317  
 318              $css = $this->stripWhitespace($css);
 319              $css = $this->shortenColors($css);
 320              $css = $this->shortenZeroes($css);
 321              $css = $this->shortenFontWeights($css);
 322              $css = $this->stripEmptyTags($css);
 323  
 324              // restore the string we've extracted earlier
 325              $css = $this->restoreExtractedData($css);
 326  
 327              $source = is_int($source) ? '' : $source;
 328              $parents = $source ? array_merge($parents, array($source)) : $parents;
 329              $css = $this->combineImports($source, $css, $parents);
 330              $css = $this->importFiles($source, $css);
 331  
 332              /*
 333               * If we'll save to a new path, we'll have to fix the relative paths
 334               * to be relative no longer to the source file, but to the new path.
 335               * If we don't write to a file, fall back to same path so no
 336               * conversion happens (because we still want it to go through most
 337               * of the move code, which also addresses url() & @import syntax...)
 338               */
 339              $converter = $this->getPathConverter($source, $path ?: $source);
 340              $css = $this->move($converter, $css);
 341  
 342              // combine css
 343              $content .= $css;
 344          }
 345  
 346          $content = $this->moveImportsToTop($content);
 347  
 348          return $content;
 349      }
 350  
 351      /**
 352       * Moving a css file should update all relative urls.
 353       * Relative references (e.g. ../images/image.gif) in a certain css file,
 354       * will have to be updated when a file is being saved at another location
 355       * (e.g. ../../images/image.gif, if the new CSS file is 1 folder deeper).
 356       *
 357       * @param ConverterInterface $converter Relative path converter
 358       * @param string             $content   The CSS content to update relative urls for
 359       *
 360       * @return string
 361       */
 362      protected function move(ConverterInterface $converter, $content)
 363      {
 364          /*
 365           * Relative path references will usually be enclosed by url(). @import
 366           * is an exception, where url() is not necessary around the path (but is
 367           * allowed).
 368           * This *could* be 1 regular expression, where both regular expressions
 369           * in this array are on different sides of a |. But we're using named
 370           * patterns in both regexes, the same name on both regexes. This is only
 371           * possible with a (?J) modifier, but that only works after a fairly
 372           * recent PCRE version. That's why I'm doing 2 separate regular
 373           * expressions & combining the matches after executing of both.
 374           */
 375          $relativeRegexes = array(
 376              // url(xxx)
 377              '/
 378              # open url()
 379              url\(
 380  
 381                  \s*
 382  
 383                  # open path enclosure
 384                  (?P<quotes>["\'])?
 385  
 386                      # fetch path
 387                      (?P<path>.+?)
 388  
 389                  # close path enclosure
 390                  (?(quotes)(?P=quotes))
 391  
 392                  \s*
 393  
 394              # close url()
 395              \)
 396  
 397              /ix',
 398  
 399              // @import "xxx"
 400              '/
 401              # import statement
 402              @import
 403  
 404              # whitespace
 405              \s+
 406  
 407                  # we don\'t have to check for @import url(), because the
 408                  # condition above will already catch these
 409  
 410                  # open path enclosure
 411                  (?P<quotes>["\'])
 412  
 413                      # fetch path
 414                      (?P<path>.+?)
 415  
 416                  # close path enclosure
 417                  (?P=quotes)
 418  
 419              /ix',
 420          );
 421  
 422          // find all relative urls in css
 423          $matches = array();
 424          foreach ($relativeRegexes as $relativeRegex) {
 425              if (preg_match_all($relativeRegex, $content, $regexMatches, PREG_SET_ORDER)) {
 426                  $matches = array_merge($matches, $regexMatches);
 427              }
 428          }
 429  
 430          $search = array();
 431          $replace = array();
 432  
 433          // loop all urls
 434          foreach ($matches as $match) {
 435              // determine if it's a url() or an @import match
 436              $type = (strpos($match[0], '@import') === 0 ? 'import' : 'url');
 437  
 438              $url = $match['path'];
 439              if ($this->canImportByPath($url)) {
 440                  // attempting to interpret GET-params makes no sense, so let's discard them for awhile
 441                  $params = strrchr($url, '?');
 442                  $url = $params ? substr($url, 0, -strlen($params)) : $url;
 443  
 444                  // fix relative url
 445                  $url = $converter->convert($url);
 446  
 447                  // now that the path has been converted, re-apply GET-params
 448                  $url .= $params;
 449              }
 450  
 451              /*
 452               * Urls with control characters above 0x7e should be quoted.
 453               * According to Mozilla's parser, whitespace is only allowed at the
 454               * end of unquoted urls.
 455               * Urls with `)` (as could happen with data: uris) should also be
 456               * quoted to avoid being confused for the url() closing parentheses.
 457               * And urls with a # have also been reported to cause issues.
 458               * Urls with quotes inside should also remain escaped.
 459               *
 460               * @see https://developer.mozilla.org/nl/docs/Web/CSS/url#The_url()_functional_notation
 461               * @see https://hg.mozilla.org/mozilla-central/rev/14abca4e7378
 462               * @see https://github.com/matthiasmullie/minify/issues/193
 463               */
 464              $url = trim($url);
 465              if (preg_match('/[\s\)\'"#\x{7f}-\x{9f}]/u', $url)) {
 466                  $url = $match['quotes'] . $url . $match['quotes'];
 467              }
 468  
 469              // build replacement
 470              $search[] = $match[0];
 471              if ($type === 'url') {
 472                  $replace[] = 'url('.$url.')';
 473              } elseif ($type === 'import') {
 474                  $replace[] = '@import "'.$url.'"';
 475              }
 476          }
 477  
 478          // replace urls
 479          return str_replace($search, $replace, $content);
 480      }
 481  
 482      /**
 483       * Shorthand hex color codes.
 484       * #FF0000 -> #F00.
 485       *
 486       * @param string $content The CSS content to shorten the hex color codes for
 487       *
 488       * @return string
 489       */
 490      protected function shortenColors($content)
 491      {
 492          $content = preg_replace('/(?<=[: ])#([0-9a-z])\\1([0-9a-z])\\2([0-9a-z])\\3(?:([0-9a-z])\\4)?(?=[; }])/i', '#$1$2$3$4', $content);
 493  
 494          // remove alpha channel if it's pointless...
 495          $content = preg_replace('/(?<=[: ])#([0-9a-z]{6})ff?(?=[; }])/i', '#$1', $content);
 496          $content = preg_replace('/(?<=[: ])#([0-9a-z]{3})f?(?=[; }])/i', '#$1', $content);
 497  
 498          $colors = array(
 499              // we can shorten some even more by replacing them with their color name
 500              '#F0FFFF' => 'azure',
 501              '#F5F5DC' => 'beige',
 502              '#A52A2A' => 'brown',
 503              '#FF7F50' => 'coral',
 504              '#FFD700' => 'gold',
 505              '#808080' => 'gray',
 506              '#008000' => 'green',
 507              '#4B0082' => 'indigo',
 508              '#FFFFF0' => 'ivory',
 509              '#F0E68C' => 'khaki',
 510              '#FAF0E6' => 'linen',
 511              '#800000' => 'maroon',
 512              '#000080' => 'navy',
 513              '#808000' => 'olive',
 514              '#CD853F' => 'peru',
 515              '#FFC0CB' => 'pink',
 516              '#DDA0DD' => 'plum',
 517              '#800080' => 'purple',
 518              '#F00' => 'red',
 519              '#FA8072' => 'salmon',
 520              '#A0522D' => 'sienna',
 521              '#C0C0C0' => 'silver',
 522              '#FFFAFA' => 'snow',
 523              '#D2B48C' => 'tan',
 524              '#FF6347' => 'tomato',
 525              '#EE82EE' => 'violet',
 526              '#F5DEB3' => 'wheat',
 527              // or the other way around
 528              'WHITE' => '#fff',
 529              'BLACK' => '#000',
 530          );
 531  
 532          return preg_replace_callback(
 533              '/(?<=[: ])('.implode('|', array_keys($colors)).')(?=[; }])/i',
 534              function ($match) use ($colors) {
 535                  return $colors[strtoupper($match[0])];
 536              },
 537              $content
 538          );
 539      }
 540  
 541      /**
 542       * Shorten CSS font weights.
 543       *
 544       * @param string $content The CSS content to shorten the font weights for
 545       *
 546       * @return string
 547       */
 548      protected function shortenFontWeights($content)
 549      {
 550          $weights = array(
 551              'normal' => 400,
 552              'bold' => 700,
 553          );
 554  
 555          $callback = function ($match) use ($weights) {
 556              return $match[1].$weights[$match[2]];
 557          };
 558  
 559          return preg_replace_callback('/(font-weight\s*:\s*)('.implode('|', array_keys($weights)).')(?=[;}])/', $callback, $content);
 560      }
 561  
 562      /**
 563       * Shorthand 0 values to plain 0, instead of e.g. -0em.
 564       *
 565       * @param string $content The CSS content to shorten the zero values for
 566       *
 567       * @return string
 568       */
 569      protected function shortenZeroes($content)
 570      {
 571          // we don't want to strip units in `calc()` expressions:
 572          // `5px - 0px` is valid, but `5px - 0` is not
 573          // `10px * 0` is valid (equates to 0), and so is `10 * 0px`, but
 574          // `10 * 0` is invalid
 575          // we've extracted calcs earlier, so we don't need to worry about this
 576  
 577          // reusable bits of code throughout these regexes:
 578          // before & after are used to make sure we don't match lose unintended
 579          // 0-like values (e.g. in #000, or in http://url/1.0)
 580          // units can be stripped from 0 values, or used to recognize non 0
 581          // values (where wa may be able to strip a .0 suffix)
 582          $before = '(?<=[:(, ])';
 583          $after = '(?=[ ,);}])';
 584          $units = '(em|ex|%|px|cm|mm|in|pt|pc|ch|rem|vh|vw|vmin|vmax|vm)';
 585  
 586          // strip units after zeroes (0px -> 0)
 587          // NOTE: it should be safe to remove all units for a 0 value, but in
 588          // practice, Webkit (especially Safari) seems to stumble over at least
 589          // 0%, potentially other units as well. Only stripping 'px' for now.
 590          // @see https://github.com/matthiasmullie/minify/issues/60
 591          $content = preg_replace('/'.$before.'(-?0*(\.0+)?)(?<=0)px'.$after.'/', '\\1', $content);
 592  
 593          // strip 0-digits (.0 -> 0)
 594          $content = preg_replace('/'.$before.'\.0+'.$units.'?'.$after.'/', '0\\1', $content);
 595          // strip trailing 0: 50.10 -> 50.1, 50.10px -> 50.1px
 596          $content = preg_replace('/'.$before.'(-?[0-9]+\.[0-9]+)0+'.$units.'?'.$after.'/', '\\1\\2', $content);
 597          // strip trailing 0: 50.00 -> 50, 50.00px -> 50px
 598          $content = preg_replace('/'.$before.'(-?[0-9]+)\.0+'.$units.'?'.$after.'/', '\\1\\2', $content);
 599          // strip leading 0: 0.1 -> .1, 01.1 -> 1.1
 600          $content = preg_replace('/'.$before.'(-?)0+([0-9]*\.[0-9]+)'.$units.'?'.$after.'/', '\\1\\2\\3', $content);
 601  
 602          // strip negative zeroes (-0 -> 0) & truncate zeroes (00 -> 0)
 603          $content = preg_replace('/'.$before.'-?0+'.$units.'?'.$after.'/', '0\\1', $content);
 604  
 605          // IE doesn't seem to understand a unitless flex-basis value (correct -
 606          // it goes against the spec), so let's add it in again (make it `%`,
 607          // which is only 1 char: 0%, 0px, 0 anything, it's all just the same)
 608          // @see https://developer.mozilla.org/nl/docs/Web/CSS/flex
 609          $content = preg_replace('/flex:([0-9]+\s[0-9]+\s)0([;\}])/', 'flex:$1}0%$2}', $content);
 610          $content = preg_replace('/flex-basis:0([;\}])/', 'flex-basis:0%$1}', $content);
 611  
 612          return $content;
 613      }
 614  
 615      /**
 616       * Strip empty tags from source code.
 617       *
 618       * @param string $content
 619       *
 620       * @return string
 621       */
 622      protected function stripEmptyTags($content)
 623      {
 624          $content = preg_replace('/(?<=^)[^\{\};]+\{\s*\}/', '', $content);
 625          $content = preg_replace('/(?<=(\}|;))[^\{\};]+\{\s*\}/', '', $content);
 626  
 627          return $content;
 628      }
 629  
 630      /**
 631       * Strip comments from source code.
 632       */
 633      protected function stripComments()
 634      {
 635          // PHP only supports $this inside anonymous functions since 5.4
 636          $minifier = $this;
 637          $callback = function ($match) use ($minifier) {
 638              $count = count($minifier->extracted);
 639              $placeholder = '/*'.$count.'*/';
 640              $minifier->extracted[$placeholder] = $match[0];
 641  
 642              return $placeholder;
 643          };
 644          // Moodle-specific change MDL-68191 starts.
 645          /* This was the old code:
 646          $this->registerPattern('/\n?\/\*(!|.*?@license|.*?@preserve).*?\*\/\n?/s', $callback);
 647          */
 648          // This is the new, more accurate and faster regex.
 649          $this->registerPattern('/
 650              # optional newline
 651              \n?
 652  
 653              # start comment
 654              \/\*
 655  
 656              # comment content
 657              (?:
 658                  # either starts with an !
 659                  !
 660              |
 661                  # or, after some number of characters which do not end the comment
 662                  (?:(?!\*\/).)*?
 663  
 664                  # there is either a @license or @preserve tag
 665                  @(?:license|preserve)
 666              )
 667  
 668              # then match to the end of the comment
 669              .*?\*\/\n?
 670  
 671              /ixs', $callback);
 672          // Moodle-specific change MDL-68191.
 673  
 674          $this->registerPattern('/\/\*.*?\*\//s', '');
 675      }
 676  
 677      /**
 678       * Strip whitespace.
 679       *
 680       * @param string $content The CSS content to strip the whitespace for
 681       *
 682       * @return string
 683       */
 684      protected function stripWhitespace($content)
 685      {
 686          // remove leading & trailing whitespace
 687          $content = preg_replace('/^\s*/m', '', $content);
 688          $content = preg_replace('/\s*$/m', '', $content);
 689  
 690          // replace newlines with a single space
 691          $content = preg_replace('/\s+/', ' ', $content);
 692  
 693          // remove whitespace around meta characters
 694          // inspired by stackoverflow.com/questions/15195750/minify-compress-css-with-regex
 695          $content = preg_replace('/\s*([\*$~^|]?+=|[{};,>~]|!important\b)\s*/', '$1', $content);
 696          $content = preg_replace('/([\[(:>\+])\s+/', '$1', $content);
 697          $content = preg_replace('/\s+([\]\)>\+])/', '$1', $content);
 698          $content = preg_replace('/\s+(:)(?![^\}]*\{)/', '$1', $content);
 699  
 700          // whitespace around + and - can only be stripped inside some pseudo-
 701          // classes, like `:nth-child(3+2n)`
 702          // not in things like `calc(3px + 2px)`, shorthands like `3px -2px`, or
 703          // selectors like `div.weird- p`
 704          $pseudos = array('nth-child', 'nth-last-child', 'nth-last-of-type', 'nth-of-type');
 705          $content = preg_replace('/:('.implode('|', $pseudos).')\(\s*([+-]?)\s*(.+?)\s*([+-]?)\s*(.*?)\s*\)/', ':$1($2$3$4$5)', $content);
 706  
 707          // remove semicolon/whitespace followed by closing bracket
 708          $content = str_replace(';}', '}', $content);
 709  
 710          return trim($content);
 711      }
 712  
 713      /**
 714       * Replace all occurrences of functions that may contain math, where
 715       * whitespace around operators needs to be preserved (e.g. calc, clamp)
 716       */
 717      protected function extractMath()
 718      {
 719          $functions = array('calc', 'clamp', 'min', 'max');
 720          $pattern = '/\b('. implode('|', $functions) .')(\(.+?)(?=$|;|})/m';
 721  
 722          // PHP only supports $this inside anonymous functions since 5.4
 723          $minifier = $this;
 724          $callback = function ($match) use ($minifier, $pattern, &$callback) {
 725              $function = $match[1];
 726              $length = strlen($match[2]);
 727              $expr = '';
 728              $opened = 0;
 729  
 730              // the regular expression for extracting math has 1 significant problem:
 731              // it can't determine the correct closing parenthesis...
 732              // instead, it'll match a larger portion of code to where it's certain that
 733              // the calc() musts have ended, and we'll figure out which is the correct
 734              // closing parenthesis here, by counting how many have opened
 735              for ($i = 0; $i < $length; $i++) {
 736                  $char = $match[2][$i];
 737                  $expr .= $char;
 738                  if ($char === '(') {
 739                      $opened++;
 740                  } elseif ($char === ')' && --$opened === 0) {
 741                      break;
 742                  }
 743              }
 744  
 745              // now that we've figured out where the calc() starts and ends, extract it
 746              $count = count($minifier->extracted);
 747              $placeholder = 'math('.$count.')';
 748              $minifier->extracted[$placeholder] = $function.'('.trim(substr($expr, 1, -1)).')';
 749  
 750              // and since we've captured more code than required, we may have some leftover
 751              // calc() in here too - go recursive on the remaining but of code to go figure
 752              // that out and extract what is needed
 753              $rest = $minifier->str_replace_first($function.$expr, '', $match[0]);
 754              $rest = preg_replace_callback($pattern, $callback, $rest);
 755  
 756              return $placeholder.$rest;
 757          };
 758  
 759          $this->registerPattern($pattern, $callback);
 760      }
 761  
 762      /**
 763       * Replace custom properties, whose values may be used in scenarios where
 764       * we wouldn't want them to be minified (e.g. inside calc)
 765       */
 766      protected function extractCustomProperties()
 767      {
 768          // PHP only supports $this inside anonymous functions since 5.4
 769          $minifier = $this;
 770          $this->registerPattern(
 771  
 772              '/(?<=^|[;}{])\s*(--[^:;{}"\'\s]+)\s*:([^;{}]+)/m',
 773              function ($match) use ($minifier) {
 774                  $placeholder = '--custom-'. count($minifier->extracted) . ':0';
 775                  $minifier->extracted[$placeholder] = $match[1] .':'. trim($match[2]);
 776                  return $placeholder;
 777  
 778              }
 779          );
 780      }
 781  
 782      /**
 783       * Check if file is small enough to be imported.
 784       *
 785       * @param string $path The path to the file
 786       *
 787       * @return bool
 788       */
 789      protected function canImportBySize($path)
 790      {
 791          return ($size = @filesize($path)) && $size <= $this->maxImportSize * 1024;
 792      }
 793  
 794      /**
 795       * Check if file a file can be imported, going by the path.
 796       *
 797       * @param string $path
 798       *
 799       * @return bool
 800       */
 801      protected function canImportByPath($path)
 802      {
 803          return preg_match('/^(data:|https?:|\\/)/', $path) === 0;
 804      }
 805  
 806      /**
 807       * Return a converter to update relative paths to be relative to the new
 808       * destination.
 809       *
 810       * @param string $source
 811       * @param string $target
 812       *
 813       * @return ConverterInterface
 814       */
 815      protected function getPathConverter($source, $target)
 816      {
 817          return new Converter($source, $target);
 818      }
 819  }