Workaround to CSS and JS cache woes

Here is a method I found of making it so the browser receives new CSS and Javascript files when they are changed on the server. It works by appending a timestamp parameter of when the file was last modified.

function urlmtime($url) {
   $parsed_url = parse_url($url);
   $path = $parsed_url['path'];
   if ($path[0] == "/") {
       $filename = $_SERVER['DOCUMENT_ROOT'] . "/" . $path;
   } else {
       $filename = $path;
   }
   if (!file_exists($filename)) {
       // If not a file then use the current time
       $lastModified = date('YmdHis');
   } else {
       $lastModified = date('YmdHis', filemtime($filename));
   }
   if (strpos($url, '?') === false) {
       $url .= '?ts=' . $lastModified;
   } else {
       $url .= '&ts=' . $lastModified;
   }
   return $url;
}

function include_css($css_url, $media='all') {
   // According to Yahoo, using link allows for progressive 
   // rendering in IE where as @import url($css_url) does not
   echo '<link rel="stylesheet" type="text/css" media="' .
      $media . '" href="' .
      urlmtime($css_url) . '">'."\n";
}

function include_javascript($javascript_url) {
   echo '<script type="text/javascript" src="' .
     urlmtime($javascript_url) .
     '"></script>'."\n";
}