<?php

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

// 具体策略类1
class CreditCardPayment implements PaymentStrategy {
    private $cardNumber;

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

    public function pay($amount) {
        echo "Paid $amount via credit card (Card Number: $this->cardNumber)\n";
    }
}

// 具体策略类2
class PayPalPayment implements PaymentStrategy {
    private $email;

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

    public function pay($amount) {
        echo "Paid $amount via PayPal (Email: $this->email)\n";
    }
}

// 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();

// 使用信用卡支付
$creditCardPayment = new CreditCardPayment("1234-5678-9012-3456");
$cart->setPaymentStrategy($creditCardPayment);
$cart->checkout(100);

// 使用PayPal支付
$paypalPayment = new PayPalPayment("john.doe@example.com");
$cart->setPaymentStrategy($paypalPayment);
$cart->checkout(50);