<?php
abstract class A {

    const WHAT = 'A';

    public static function call() {
        echo static::WHAT;
    }

}

class B extends A {

    const WHAT = 'B';

}

$method = new ReflectionMethod("b::call");
$method->invoke(null);
$method->invokeArgs(null, array());
$method = new ReflectionMethod("A::call");
$method->invoke(null);
$method->invokeArgs(null, array());
?>