PHP 函数设计模式应用案例分析

class DatabaseConnection {  private static $instance;  private function __construct() {}  public static function getInstance() {    if (!isset(self::$instance)) {      self::$instance = new self();    }    return self::$instance;  }}// 获取数据库连接$connection = DatabaseConnection::getInstance();

interface Shape {  public function draw();}class Circle implements Shape {  public function draw() { echo "Drawing a circle"; }}class Square implements Shape {  public function draw() { echo "Drawing a square"; }}class ShapeFactory {  public static function create($type) {    switch ($type) {      case 'circle': return new Circle();      case 'square': return new Square();      default: throw new Exception('Invalid shape type');    }  }}// 创建一个圆形$circle = ShapeFactory::create('circle');$circle->draw(); // 输出：Drawing a circle

class Subject {  private $observers = [];  public function attach($observer) {    $this->observers[] = $observer;  }  public function notify() {    foreach ($this->observers as $observer) {      $observer->update($this);    }  }}class Observer {  public function update($subject) {    echo "Observer notified";  }}// 创建一个主题和两个观察者$subject = new Subject();$observer1 = new Observer();$observer2 = new Observer();// 将观察者附加到主题$subject->attach($observer1);$subject->attach($observer2);// 当主题的状态发生改变时，通知所有观察者$subject->notify(); // 输出：Observer notifiedObserver notified

interface PaymentStrategy {  public function calculateTotal($order);}class CashPaymentStrategy implements PaymentStrategy {  public function calculateTotal($order) {    return $order->getTotal();  }}class CreditCardPaymentStrategy implements PaymentStrategy {  public function calculateTotal($order) {    return $order->getTotal() + 0.03 * $order->getTotal(); // 应用 3% 费用  }}// 创建一个订单和选择一种支付策略$order = new Order();$order->setTotal(100);$strategy = new CreditCardPaymentStrategy();// 使用策略计算总额$total = $strategy->calculateTotal($order); // 输出：103