General Polymorphism with PHP examples

Question

As only Dogs can play \"fetch\", is this example a good or a bad idea? I suspect it\'s a really bad idea due to the usage of instanceof, but I\'m not entirely sure why.

Answer 1

Another example for Polymorphism in PHP

    width = $width;
      $this->height = $height;
   }

   public function getArea(){
      return $this->width * $this->height;
   }
}

class Circle implements Shape {
   private $radius;

   public function __construct($radius) {
      $this->radius = $radius;
   }

   public function getArea(){

      return 3.14 * $this->radius * $this->radius;
   }
}

function calculateArea(Shape $shape) {
   return $shape->getArea();
}

$square = new Square(5, 5);
$circle = new Circle(7);

echo calculateArea($square), "
";
echo calculateArea($circle);
?>