PHP中如何使用抽象类和接口来管理和操作自定义的数据类型

abstract class Shape {
    protected $name;
    
    public function __construct($name) {
        $this->name = $name;
    }
    
    abstract public function area();
    
    public function displayName() {
        echo "This shape is a " . $this->name . ".
";
    }
}

class Circle extends Shape {
    private $radius;
    
    public function __construct($name, $radius) {
        parent::__construct($name);
        $this->radius = $radius;
    }
    
    public function area() {
        return 3.14 * $this->radius * $this->radius;
    }
}

class Triangle extends Shape {
    private $base;
    private $height;
    
    public function __construct($name, $base, $height) {
        parent::__construct($name);
        $this->base = $base;
        $this->height = $height;
    }
    
    public function area() {
        return 0.5 * $this->base * $this->height;
    }
}

$circle = new Circle("circle", 5);
$triangle = new Triangle("triangle", 4, 6);

$circle->displayName();
echo "Area of circle: " . $circle->area() . "
";

$triangle->displayName();
echo "Area of triangle: " . $triangle->area() . "
";

interface ProductInterface {
    public function getName();
    public function getPrice();
}

class Product implements ProductInterface {
    private $name;
    private $price;
    
    public function __construct($name, $price) {
        $this->name = $name;
        $this->price = $price;
    }
    
    public function getName() {
        return $this->name;
    }
    
    public function getPrice() {
        return $this->price;
    }
}

class Book implements ProductInterface {
    private $name;
    private $price;
    private $author;
    
    public function __construct($name, $price, $author) {
        $this->name = $name;
        $this->price = $price;
        $this->author = $author;
    }
    
    public function getName() {
        return $this->name;
    }
    
    public function getPrice() {
        return $this->price;
    }
    
    public function getAuthor() {
        return $this->author;
    }
}

$product = new Product("generic product", 10);
$book = new Book("PHP basics", 20, "John Doe");

echo "Product: " . $product->getName() . ", Price: " . $product->getPrice() . "
";
echo "Book: " . $book->getName() . ", Price: " . $book->getPrice() . ", Author: " . $book->getAuthor() . "
";