php function to minify javascript and css

$css = '';
$root = $_SERVER['DOCUMENT_ROOT'].'/css/'; //directory where the css lives
$files = explode(',',$_SERVER['QUERY_STRING']);
if(sizeof($files))
{
	foreach($files as $file)
	{
		$css.= (is_file($root.$file.'.css') ? file_get_contents($root.$file.'.css') : '');
	}
}
return str_replace('; ',';',str_replace(' }','}',str_replace('{ ','{',str_replace(array("\r\n","\r","\n","\t",'  ','    ','    '),"",preg_replace('!/\*[^*]*\*+([^/][^*]*\*+)*/!','',$css)))));