This will be always true ? Can this change in php 7 for example ?

Yup. Afterall, the tests are passing with php7 and even hhvm, so... And this should not change IMo, it's been there as long as object support was there so...

ok so let's go we will see in few year if it's still the case.

weird. @Taluu where are you find this hack ?

during a simple (array) $object export :}

and some other things can't remember which too (I think it was in the var_dumper component of symfony)

Maybe I should check up with https://github.com/symfony/var-dumper/blob/master/Caster/Caster.php though, but then I would reintroduce some reflection...