public function addSearchPath($paths, $append = false)
    {
        settype($paths, 'array');

        foreach ($paths as $path) {
            if (empty($path)) {
                continue;
            }

            if (in_array($path, $this->_search_paths)) {
                continue;
            }

            if ($append) {
                $this->_search_paths[] = $path;
            } else {
                array_unshift($this->_search_paths, $path);
            }
        }
    }