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 {
     //
    public const C = 3;
}

?>

Documentation

Related : Final Keyword

Added in PHP 8.1