Change $key from private to protected

[Externaluse]

Might there be a chance to change the $key property to protected? Another project (https://github.com/cruxinator/php-bitmask) is using it for extension. I've written my own changes to their bitmask but it's irritating to have two key properties in set_state - although this is mainly relevant for debugging, is there any reason that $key needs to be private?

::__set_state(array( 'value' => 9437184, 'key' => 'SomeEnumValue', 'key' => 'SomeEnumValue|AnotherEnumValue',