[depp]

class First {
	protected static $number = "First";
	protected function getNumber() {
		return $this->number;
	}
}

class Second extends First {
	protected static $number = "Second";
	public function getNumber() {
		return parent::$number;
	}
}

$first = new First;
$second = new Second;
// здесь нужно вывести "First"
echo $second->getNumber();