PHP におけるクラスの継承とポリモーフィズム

class Animal {
   // 父类属性和方法
   public $name;
   public function __construct($name) {
      $this->name = $name;
   }
   public function makeSound() {
      echo "Animal is making sound";
   }
}
class Dog extends Animal {
    // 子类新增属性和方法
    public function bark() {
        echo "Dog is barking";
    }
}

$dog = new Dog("Fido");
echo $dog->name; // 输出 "Fido"
$dog->makeSound(); // 输出 "Animal is making sound"
$dog->bark(); // 输出 "Dog is barking"

class Animal {
    public function makeSound() {
        echo "Animal is making sound";
    }
}

class Cat extends Animal {
    public function makeSound() {
        echo "Cat is meowing";
    }
}

$cat = new Cat();
$cat->makeSound(); // 输出 "Cat is meowing"

class Animal {
    public function makeSound() {
        echo "Animal is making sound";
    }
}

class Dog extends Animal {
    public function makeSound() {
        echo "Dog is barking";
    }
}

class Cat extends Animal {
    public function makeSound() {
        echo "Cat is meowing";
    }
}

function makeAnimalSound(Animal $animal) {
    $animal->makeSound();
}

$dog = new Dog();
$cat = new Cat();

makeAnimalSound($dog); // 输出 "Dog is barking"
makeAnimalSound($cat); // 输出 "Cat is meowing"