The right way to get result value in string format is only using the __toString() ?

[BenMorel]

If I understand your question correctly, yes.

This is a magic method though, to be used for casting to string:

$a = BigDecimal::of('12.34');
$string = (string) $a; // equivalent to $a->__toString();

If I did not understand your question, please reformulate it.

[XavierTecBr]

Yes this is it. Thanks so much.