设计模式是一套被反复使用、多数人知晓的、经过分类编目的、代码设计经验的总结。在PHP中,常用的设计模式有许多,以下是一些常见的设计模式:
1. 单例模式(Singleton Pattern)
确保一个类只有一个实例,并提供全局访问点。
class Singleton {
private static $instance;
private function __construct() {}
public static function getInstance() {
if (self::$instance === null) {
self::$instance = new self();
}
return self::$instance;
}
}
2. 工厂模式(Factory Pattern)
定义一个用于创建对象的接口,让子类决定实例化哪一个类。
interface Shape {
public function draw();
}
class Circle implements Shape {
public function draw() {
echo "Draw a Circle";
}
}
class Square implements Shape {
public function draw() {
echo "Draw a Square";
}
}
class ShapeFactory {
public function getShape($type) {
switch ($type) {
case 'circle':
return new Circle();
case 'square':
return new Square();
default:
return null;
}
}
}
3. 观察者模式(Observer Pattern)
定义了一种一对多的依赖关系,让多个观察者对象同时监听某一个主题对象。
interface Observer {
public function update($message);
}
class ConcreteObserver implements Observer {
public function update($message) {
echo "Received message: $message";
}
}
class Subject {
private $observers = [];
public function addObserver(Observer $observer) {
$this->observers[] = $observer;
}
public function notifyObservers($message) {
foreach ($this->observers as $observer) {
$observer->update($message);
}
}
}
4. 策略模式(Strategy Pattern)
定义一系列的算法,把它们封装起来,并使它们可以相互替换。
interface PaymentStrategy {
public function pay($amount);
}
class CreditCardPayment implements PaymentStrategy {
public function pay($amount) {
echo "Paid $amount via Credit Card";
}
}
class PayPalPayment implements PaymentStrategy {
public function pay($amount) {
echo "Paid $amount via PayPal";
}
}
class ShoppingCart {
private $paymentStrategy;
public function setPaymentStrategy(PaymentStrategy $paymentStrategy) {
$this->paymentStrategy = $paymentStrategy;
}
public function checkout($amount) {
$this->paymentStrategy->pay($amount);
}
}
5. 装饰器模式(Decorator Pattern)
动态地给一个对象添加一些额外的职责。
interface Coffee {
public function cost();
}
class SimpleCoffee implements Coffee {
public function cost() {
return 5;
}
}
class MilkDecorator implements Coffee {
private $coffee;
public function __construct(Coffee $coffee) {
$this->coffee = $coffee;
}
public function cost() {
return $this->coffee->cost() + 2;
}
}
这只是几个PHP中常见的设计模式,设计模式是一种通用的解决问题的思想,根据实际需求选择合适的设计模式来提高代码的可维护性和可扩展性。
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