3.8. Strategy¶

1<?php
2
3interface DiscountStrategy
4{
5    public function calculateDiscount($price): float;
6}

 1<?php
 2
 3class SilverDiscount implements DiscountStrategy
 4{
 5    public function calculateDiscount($price): float
 6    {
 7        return $price * 0.1; // 10% discount for silver members
 8    }
 9}
10
11class GoldDiscount implements DiscountStrategy
12{
13    public function calculateDiscount($price): float
14    {
15        return $price * 0.2; // 20% discount for gold members
16    }
17}
18
19class PlatinumDiscount implements DiscountStrategy
20{
21    public function calculateDiscount($price): float
22    {
23        return $price * 0.3; // 30% discount for platinum members
24    }
25}

 1<?php
 2
 3class ShoppingCart
 4{
 5    private DiscountStrategy $discountStrategy;
 6    private array $items = [];
 7
 8    public function addItem(Item $item): void
 9    {
10        $this->items[] = $item;
11    }
12
13    public function setDiscountStrategy(DiscountStrategy $discountStrategy): void
14    {
15        $this->discountStrategy = $discountStrategy;
16    }
17
18    public function calculateTotal(): float|int
19    {
20        $subtotal = 0;
21        foreach ($this->items as $item) {
22            $subtotal += $item->price;
23        }
24        $discount = $this->discountStrategy->calculateDiscount($subtotal);
25
26        return $subtotal - $discount;
27    }
28}

 1<?php
 2
 3class Item
 4{
 5    public string $name;
 6    public float $price;
 7
 8    public function __construct($name, $price)
 9    {
10        $this->name = $name;
11        $this->price = $price;
12    }
13}
14
15// Create a shopping cart
16$cart = new ShoppingCart();
17
18// Add items to the cart
19$item1 = new Item('Widget', 10.00);
20$item2 = new Item('Gadget', 5.00);
21$cart->addItem($item1);
22$cart->addItem($item2);
23
24// Calculate discounts based on customer's membership level
25if ($customer->isSilver()) {
26    $cart->setDiscountStrategy(new SilverDiscount());
27} elseif ($customer->isGold()) {
28    $cart->setDiscountStrategy(new GoldDiscount());
29} elseif ($customer->isPlatinum()) {
30    $cart->setDiscountStrategy(new PlatinumDiscount());
31}
32
33// Calculate total with discount
34$total = $cart->calculateTotal();