@dgoosens
https://wiki.php.net/rfc/readonly_properties :
"There is currently no way to make a property readable to everyone and writeable only to the containing object, with PHP's visibility specifiers allowing all or nothing: a scope can either both read and write, or do neither. While __get and __set exist, these do not actually allow control of the same property, merely only exposing a separate property, and they are only usable for undeclared properties, which cannot be reflected and are not performant."