class aParent {
  static private $classname = __CLASS__;

  static function my_classname() {
    return self::$classname;
  }
}

class aChild extends aParent {
  static public $classname = __CLASS__;

  static public function my_classname() {
    return self::$classname;
  }
}

$child = new aChild;
echo $child->my_classname(); # this gives me 'Parent'

echo "\n";
echo aChild::my_classname();
echo "\n";