protected function quotedString($stopchars) {
        $tok = $this->scanner->current();
        if ($tok == '"' || $tok == "'") {
            $this->scanner->next();
            $ret = $this->scanner->charsUntil($tok . $stopchars);
            if ($this->scanner->current() == $tok) {
                $this->scanner->next();
            } else {
                // Parse error because no close quote.
                $this->parseError("Expected %s, got %s", $tok, $this->scanner->current());
            }
            return $ret;
        }
        return false;
    }