<?php

final class A
{
    private mixed $private;
    private private(set) mixed $privatePrivateSet;
    protected private(set) mixed $protectedPrivateSet;
    public private(set) mixed $publicPrivateSet;
}

var_dump(
    new ReflectionProperty(A::class, 'private')->isPrivateSet(),
    new ReflectionProperty(A::class, 'privatePrivateSet')->isPrivateSet(),
    new ReflectionProperty(A::class, 'protectedPrivateSet')->isPrivateSet(),
    new ReflectionProperty(A::class, 'publicPrivateSet')->isPrivateSet(),
);