PHPで親クラスから子クラスの関数を呼び出す方法は?

<code class="php">class whale
{
  public function __construct()
  {
    // some code here
  }

  public function myfunc()
  {
    // How do I call the "test" function of the fish class here?
  }
}

class fish extends whale
{
  public function __construct()
  {
    parent::__construct();
  }

  public function test()
  {
    echo "So you managed to call me !!";
  }
}</code>

<code class="php">abstract class whale
{
  public function __construct()
  {
    // some code here
  }

  public function myfunc()
  {
    $this->test();
  }

  abstract public function test();
}

class fish extends whale
{
  public function __construct()
  {
    parent::__construct();
  }

  public function test()
  {
    echo "So you managed to call me !!";
  }
}

$fish = new fish();
$fish->test();
$fish->myfunc();</code>