Group multiple media queries formed as output of LESS css

Question

I was planning to use LESS css in my project (PHP). I am planning to use its nested @media query feature. I find that it fails to group the multiple media queries in the output css it generates.

For example:

// LESS
.header {
  @media all and (min-width: 240px) and (max-width: 319px) {
    font-size: 12px;
  }

  @media all and (min-width: 320px) and (max-width: 479px) {
    font-size: 16px;
    font-weight: bold;
  }
}

.body {
  @media all and (min-width: 240px) and (max-width: 319px) {
    font-size: 10px;
  }

  @media all and (min-width: 320px) and (max-width: 479px) {
    font-size: 12px;
  }
}

// output CSS
@media all and (min-width: 240px) and (max-width: 319px) {
  .header {
    font-size: 12px;
  }
}
@media all and (min-width: 320px) and (max-width: 479px) {
  .header {
    font-size: 16px;
    font-weight: bold;
  }
}
@media all and (min-width: 240px) and (max-width: 319px) {
  .body {
    font-size: 10px;
  }
}
@media all and (min-width: 320px) and (max-width: 479px) {
  .body {
    font-size: 12px;
  }
}

My expected output is (@media queries grouped)

@media all and (min-width: 240px) and (max-width: 319px) {
  .header {
    font-size: 12px;
  }
  .body {
    font-size: 10px;
  }
}
@media all and (min-width: 320px) and (max-width: 479px) {
  .header {
    font-size: 16px;
    font-weight: bold;
  }
  .body {
    font-size: 12px;
  }
}

I would like to know if it can be done in LESS (PHP) it self or is there any simple PHP based CSS parser I can use to manipulate the output CSS to group and merge the @media queries. as shown in the below flow.

  LESS file
      |
      V
[LESSphp compiler]
      |
      V
   CSS file
      |
      V
The CSS file generated
would undergo my script
written using CSS parser
      |
      V
   CSS file
with similar @media
grouped.

In case achieving grouped @media queries in LESS (PHP) is not an option I would like to know your suggestions on CSS parser (PHP) that can be used in the above flow.

It can't do this - it can't guarentee one media query will be matched and another one won't and whether one selector will override another one. — Luke Page
If it is not possible to do it in LESS itself then I would like to know if there are any simple CSS parsers in PHP using which I can manipulate the output file so that I will programmatically achieve this. — Goje87

webevolutis webevolutis · Accepted Answer · 2013-08-12T16:24:06

I adapt autoCompileLess function to group media query at the end of CSS without changing the less code.

@mobile: ~"only screen and (max-width: 529px)";
.test {
    color:green;
    @media @mobile { color:red; }
}    
.test2 {
    color:red;
    @media @mobile { color:blue; }
}

Compile with less by default

.test {
    color:green;
}    
.test2 {
    color:red;
}
@media only screen and (max-width: 529px) {
    .test {
        color:red;
    }
}    
@media only screen and (max-width: 529px) {
    .test2 {
        color:blue;
    }
}

Compile less with the following function

.test {
    color:green;
}    
.test2 {
    color:red;
}
@media only screen and (max-width: 529px) {
    .test {
        color:red;
    }
    .test2 {
        color:blue;
    }
}

And the function :

<?php
function autoCompileLess($inputFile, $outputFile)
{
    // load cache
    $cacheFile = $inputFile.".cache";

    if (file_exists($cacheFile))
    {
        $cache = unserialize(file_get_contents($cacheFile));
        if (empty($cache)) $cache = $inputFile;
    }
    else
    {
        $cache = $inputFile;
    }

    // compile less
    $less = new lessc;
    $newCache = $less->cachedCompile($cache);

    // save less cache
    $saveCache = $newCache;

    // search media query in CSS
    preg_match_all('#@media(.*?)\{(.+?}[ \n])\}#si',$newCache['compiled'],$match,PREG_SET_ORDER);//$MatchingString now hold all strings matching $pattern.


    $media = array();

    // group same media query
    foreach ($match as $val)
    {
        if (!isset($media[$val[1]])) $media[$val[1]] = '';

        $media[$val[1]] .= $val[2];
    }

    // delete media query of cache
    $newCache['compiled'] = preg_replace('#@media(.*?)\{(.+?}[ \n])\}#si', '', $newCache['compiled']);

    // add groups of media query at the end of CSS
    $final = $newCache['compiled'] . "\n";
    foreach ($media as $id => $val)
    {
        $final .= "\n" . '@media' . $id . '{' . $val . '}' . "\n";
    }

    // save less
    // save CSS with groups of media query
    if (!is_array($cache) || $newCache["updated"] > $cache["updated"]) 
    {
        file_put_contents($cacheFile, serialize($saveCache));
        // file_put_contents($outputFile, $newCache['compiled']);
        file_put_contents($outputFile, $final);
    }
}

// use of function
autoCompileLess('style.less', 'style.css');

Group multiple media queries formed as output of LESS css

2 Answers