function getTokenString($start_offset = 0, $end_offset = 0) {
		$token_start = ((is_int($this->token_start)) ? $this->token_start : $this->pos) + $start_offset;
		$len = $this->pos - $token_start + 1 + $end_offset;
		return (($len > 0) ? substr($this->doc, $token_start, $len) : '');
	}