protected function _addConstants($constants)
    {
        foreach ($constants as $key => $value) {
            if (is_resource($value) === false) {
                if (is_array($value) || strpos($value, DIRECTORY_SEPARATOR) === false) {
                    continue;
                }
                if ($value !== DIRECTORY_SEPARATOR && !@file_exists($value)) {
                    continue;
                }
                $this->constantMap[$key] = rtrim($value, DIRECTORY_SEPARATOR);
            }
        }
        ksort($this->constantMap);
    }