Currently, class constants are always overridable by child classes

<?php
class Universe
{
    *final* public const SPEED_OF_LIGHT = 299_458_792;
}
class RingSpace extends Universe
{
    public const SPEED_OF_LIGHT = 12_758;
}

Fatal error: RingSpace::SPEED_OF_LIGHT cannot override
    final constant Universe::SPEED_OF_LIGHT