$this->digest_header = null;

            if (!empty($this->server['PHP_AUTH_DIGEST'])) {

                $this->digest_header = substr($this->server['PHP_AUTH_DIGEST'],

                                              strpos($this->server['PHP_AUTH_DIGEST'],' ')+1);

            } else {

                $headers = getallheaders();

                if(isset($headers['Authorization']) && !empty($headers['Authorization'])) {

                    $this->digest_header = substr($headers['Authorization'],

                                                  strpos($headers['Authorization'],' ')+1);

                }

            }