PHP override class constants

class_constants.php

<?php

class Foo
{
    const TEST = 'foo';

    public static function getConst()
    {
        return static::TEST;
    }

    public function get_const()
    {
        return static::TEST;
    }
}

class Bar extends Foo
{
    const TEST = 'bar';
}

echo Foo::TEST; // foo
echo Bar::TEST; // bar

echo Foo::getConst(); // foo
echo Bar::getConst(); // bar

$foo = new Foo();
$bar = new Bar();

echo $foo->get_const(); // foo
echo $bar->get_const(); // bar

Useful, thanks!