Flow\Parser::parseLiteralExpression PHP Method

    protected function parseLiteralExpression()
    {
        $token = $this->stream->getCurrentToken();
        switch ($token->getType()) {
            case Token::CONSTANT:
                $this->stream->next();
                switch ($token->getValue()) {
                    case 'true':
                        $node = new Expression\ConstantExpression(true, $token->getLine());
                        break;
                    case 'false':
                        $node = new Expression\ConstantExpression(false, $token->getLine());
                        break;
                    case 'null':
                        $node = new Expression\ConstantExpression(null, $token->getLine());
                        break;
                }
                break;
            case Token::NUMBER:
                $this->stream->next();
                if (preg_match('/\\./', $token->getValue())) {
                    $node = new Expression\ConstantExpression(floatval($token->getValue()), $token->getLine());
                } else {
                    $node = new Expression\ConstantExpression(intval($token->getValue()), $token->getLine());
                }
                break;
            case Token::STRING:
                $this->stream->next();
                $node = new Expression\StringExpression(strval($token->getValue()), $token->getLine());
                break;
            default:
                throw new SyntaxError(sprintf('unexpected "%s", expecting an expression', str_replace("\n", '\\n', $token->getValue())), $token);
        }
        return $this->parsePostfixExpression($node);
    }