private function getConstant()
    {
        $identifier = $this->getIdentifier();
        $tokens = array();

        // check for a special constant type
        switch (strtolower($identifier)) {
            case 'true':
                $tokens[] = array(DocLexer::T_TRUE, $identifier);
                break;
            case 'false':
                $tokens[] = array(DocLexer::T_FALSE, $identifier);
                break;
            case 'null':
                $tokens[] = array(DocLexer::T_NULL, $identifier);
                break;
            default:
                $tokens[] = array(DocLexer::T_IDENTIFIER, $identifier);
        }

        return $tokens;
    }