PHP中如何实现策略模式？

// 定义策略接口
interface PaymentStrategy {
    public function pay($amount);
}

// 具体策略类 - 信用卡支付
class CreditCardStrategy implements PaymentStrategy {
    private $name;
    private $cardNumber;
    private $cvv;
    private $dateOfExpiry;

    public function __construct($name, $cardNumber, $cvv, $dateOfExpiry) {
        $this->name = $name;
        $this->cardNumber = $cardNumber;
        $this->cvv = $cvv;
        $this->dateOfExpiry = $dateOfExpiry;
    }

    public function pay($amount) {
        echo "Paid {$amount} using credit/debit card";
    }
}

// 具体策略类 - 支付宝支付
class AlipayStrategy implements PaymentStrategy {
    private $emailId;
    private $password;

    public function __construct($emailId, $password) {
        $this->emailId = $emailId;
        $this->password = $password;
    }

    public function pay($amount) {
        echo "Paid {$amount} using Alipay";
    }
}

// 上下文类
class ShoppingCart {
    private $paymentStrategy;

    public function setPaymentStrategy(PaymentStrategy $paymentStrategy) {
        $this->paymentStrategy = $paymentStrategy;
    }

    public function checkout($amount) {
        $this->paymentStrategy->pay($amount);
    }
}

// 客户端代码
$cart = new ShoppingCart();

$cart->setPaymentStrategy(new CreditCardStrategy("John Doe", "1234567890123456", "123", "12/23"));
$cart->checkout(100);

$cart->setPaymentStrategy(new AlipayStrategy("john.doe@example.com", "password123"));
$cart->checkout(200);

class WeChatPayStrategy implements PaymentStrategy {
    private $openId;

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

    public function pay($amount) {
        echo "Paid {$amount} using WeChat Pay";
    }
}

// 使用新的策略
$cart->setPaymentStrategy(new WeChatPayStrategy("wechat_open_id"));
$cart->checkout(300);