Regular expression that will only compress certain sections of the page

I have a function that strips out un-needed whitespaces from the output of my php page prior to saving the page to an HTML file for caching purposes.

However in some sections of my page I have source code in pre tags and these whitespaces effect how the code is displayed. My skill with regular expressions is horrible so I am basically look for a solution to stop this function from messing with code inside:

 <pre></pre>

This is the php function

function sanitize_output($buffer)
   {
      $search = array(
         '/\>[^\S]+/s', //strip whitespaces after tags, except space
         '/[^\S ]+\</s', //strip whitespaces before tags, except space
         '/(\s)+/s',  // shorten multiple whitespace sequences
           );
      $replace = array(
         '>',
         '<',
         '\\1',
         );
    $buffer = preg_replace($search, $replace, $buffer);
      return $buffer;
   }

Thanks for your help.

Heres what i found to be working :

Solution:

function stripBufferSkipPreTags($buffer){
$poz_current = 0;
$poz_end = strlen($buffer)-1;
$result = "";

while ($poz_current < $poz_end){
    $t_poz_start = stripos($buffer, "<pre", $poz_current);
    if ($t_poz_start === false){
        $buffer_part_2strip = substr($buffer, $poz_current);
        $temp = stripBuffer($buffer_part_2strip);
        $result .= $temp;
        $poz_current = $poz_end;
    }
    else{
        $buffer_part_2strip = substr($buffer, $poz_current, $t_poz_start-$poz_current);
        $temp = stripBuffer($buffer_part_2strip);
        $result .= $temp;
   开发者_运维问答     $t_poz_end = stripos($buffer, "</pre>", $t_poz_start);
        $temp = substr($buffer, $t_poz_start, $t_poz_end-$t_poz_start);
        $result .= $temp;
        $poz_current = $t_poz_end;
    }
}
return $result;

}

function stripBuffer($buffer){
// change new lines and tabs to single spaces
$buffer = str_replace(array("\r\n", "\r", "\n", "\t"), ' ', $buffer);
// multispaces to single...
$buffer = preg_replace(" {2,}", ' ',$buffer);
// remove single spaces between tags
$buffer = str_replace("> <", "><", $buffer);
// remove single spaces around &nbsp;
$buffer = str_replace(" &nbsp;", "&nbsp;", $buffer);
$buffer = str_replace("&nbsp; ", "&nbsp;", $buffer);
return $buffer;

}

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Regular expressions are known to be evil (see this and this) when it comes to parsing HTML.

That said, try to do what you need in another way, like using a DOM parser and customizing its HTML output functions.

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If you are compressing for disk-space, you should consider using gz compression. (php.net/gz_deflate)