Folder::modified PHP Method

    public function modified($format = null, $handler = 'date')
    {
        $modified = filemtime($this->root);
        $items = $this->scan(array('.', '..'));
        foreach ($items as $item) {
            if (is_file($this->root . DS . $item)) {
                $newModified = filemtime($this->root . DS . $item);
            } else {
                $object = new static($this->root . DS . $item);
                $newModified = $object->modified();
            }
            $modified = $newModified > $modified ? $newModified : $modified;
        }
        return !is_null($format) ? $handler($format, $modified) : $modified;
    }

 /**
  * Recursively check when the dir and all
  * subfolders have been modified for the last time.
  *
  * @param   string   $dir The path of the directory
  * @param   string   $format
  * @return  int
  */
 public static function modified($dir, $format = null)
 {
     // It's easier to handle this with the Folder class
     $object = new Folder($dir);
     return $object->modified($format);
 }