Final Class Constants

Using the final option with class constants, the constant cannot be redefined by a child class. It is not possible to give it a new value or visibility.

It yields a fatal error: y::x cannot override final constant.

<?php

    class X {
        final public const F = 1;
        public const C = 2;
    }

    class Y extends X {
        // this is an error
        public const C = 3;
    }

?>

Documentation

Related : Final Keyword

Added in PHP 8.1