PHP 对象导向编程进阶：理解多态和继承

class Animal {
    public function speak() {
        echo "Animal speaks\n";
    }
}

class Dog extends Animal {
    public function speak() {
        echo "Dog barks\n";
    }
}

class Cat extends Animal {
    public function speak() {
        echo "Cat meows\n";
    }
}

$dog = new Dog();
$dog->speak();  // 输出：Dog barks

$cat = new Cat();
$cat->speak();  // 输出：Cat meows

class Person {
    protected $name;
    protected $age;

    public function __construct($name, $age) {
        $this->name = $name;
        $this->age = $age;
    }

    public function getName() {
        return $this->name;
    }
}

class Employee extends Person {
    private $salary;

    public function __construct($name, $age, $salary) {
        parent::__construct($name, $age);  // 调用父类构造函数
        $this->salary = $salary;
    }

    public function getSalary() {
        return $this->salary;
    }
}

$employee = new Employee("John Doe", 30, 50000);
echo "Employee name: " . $employee->getName() . "\n";
echo "Employee salary: " . $employee->getSalary() . "\n";

class Fruit {
    protected $name;

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

    public function getName() {
        return $this->name;
    }
}

class Kiwi extends Fruit {
    public function __construct() {
        parent::__construct("Kiwi");
    }
}

$kiwi = new Kiwi();
echo "Fruit name: " . $kiwi->getName() . "\n";

class Car {
    protected $make;
    protected $model;

    public function __construct($make, $model) {
        $this->make = $make;
        $this->model = $model;
    }

    public function getType() {
        return "Car";
    }
}

class SportsCar extends Car {
    public function getType() {
        return "Sports Car";
    }
}

$car = new Car("Toyota", "Camry");
$sportsCar = new SportsCar("Ferrari", "F430");

echo "Car type: " . $car->getType() . "\n";
echo "Sports car type: " . $sportsCar->getType() . "\n";