Помогите с задачей. ООП, PHP

<?php
class Mouse {
 function pisk() {
   echo "Pi-pi-pi!";
 }
}

class WildCat {
 function meow() {
   echo "Meow!";
 }
}

class HomeCat extends WildCat
{
function catchMouse($mouse)
 if ($mouse instanceof Mouse) {
  echo 'Mouse is catched succesfully!';
 } else {
   echo 'It is not mouse!';
 }
}

?>