PHP의 상위 클래스에서 하위 클래스 메소드에 액세스하는 방법은 무엇입니까?

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

  function myfunc()
  {
    // how do i call the "test" function of fish class here??
  }
}

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

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

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

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

  abstract function test();
}

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

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