Aren't the constructor checks redundant here? They would never get through the has/is/get checks, or is it done simply because of performance reasons?

Personally I would like to see a guard clause here for readability:

if ($reflMethod->getNumberOfRequiredParameters() >0) {continue;}// also prevents a lot of is checks as destructor is hardly ever implemented and constructor only ever once

Another option would be to omit the number of required attributes at this point and only check it when needed.

$attributes[lcfirst(substr($name,3))] =0 ===$reflMethod->getNumberOfRequiredParameters();

This would limit the checks even more, but I'm not sure if calling the reflection method is slower or relying ongetName() andstrpos()

If it comes down to preferences, feel free to ignore if you disagree

you should not assign false here. It could corrupt the cache in case an exception is thrown in the following logic, is catched, and the method is called again: as you assign false in the cache array, the cache is set and used on future calls (and breaks the contracts of the method). Use a local variable and assign the cache only on next line when using the value.

and the logic is also altered here: an empty array should be returned here. Onlyfalse triggers the fallback logic. So you need to use a strict comparison

btw, this means we are missing a test covering the case where the object does not have any property serialized in the groups being used (your PR switches it to serialize the whole object, which is a regression)