Eliminating Code Duplication: A Practical Guide to PHP Design Patterns

Factory method pattern

PHP design patterns are the key to improving code quality and maintainability. In actual development, eliminating code duplication is a crucial step. This article by PHP editor Yuzai provides you with a practical guide to PHP design patterns to help you understand how to use design patterns to effectively eliminate code duplication, improve code readability and maintainability, and make your project more efficient and stable. Whether you are a PHP beginner or an experienced developer, this article will bring you practical tips and advice to make your code more elegant and streamlined.

interface Product
{
public function operation();
}

class ConcreteProductA implements Product
{
public function operation()
{
// ...
}
}

class ConcreteProductB implements Product
{
public function operation()
{
// ...
}
}

class Creator
{
public function factoryMethod(): Product
{
return new ConcreteProductA(); // 可根据需要返回不同的具体产品
}
}

$product = (new Creator())->factoryMethod();
$product->operation();

Single case mode

The singleton pattern ensures that the class can only be instantiated once. This is useful for controlling global state or resource access.

class Singleton
{
private static $instance;

private function __construct() {}
private function __clone() {}
private function __wakeup() {}

public static function getInstance(): Singleton
{
if (self::$instance === null) {
self::$instance = new Singleton();
}

return self::$instance;
}
}

$instance1 = Singleton::getInstance();
$instance2 = Singleton::getInstance();

if ($instance1 === $instance2) {
// 始终返回同一个实例
}

Strategy Mode

The Strategy pattern defines a set of related algorithms and makes them easily interchangeable. This is a good practice when we need to modify the behavior of the algorithm based on different scenarios.

interface Strategy
{
public function operation();
}

class ConcreteStrategyA implements Strategy
{
public function operation()
{
// ...
}
}

class ConcreteStrategyB implements Strategy
{
public function operation()
{
// ...
}
}

class Context
{
private $strategy;

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

public function executeStrategy()
{
$this->strategy->operation();
}
}

$context = new Context(new ConcreteStrategyA());
$context->executeStrategy(); // 使用策略 A

$context = new Context(new ConcreteStrategyB());
$context->executeStrategy(); // 使用策略 B

Observer Pattern

The observer pattern defines an object (subject) that can store a set of objects (observers) that depend on it. When a topic's state changes, it automatically notifies all observers.

interface Subject
{
public function attach(Observer $observer);
public function detach(Observer $observer);
public function notify();
}

class ConcreteSubject implements Subject
{
private $observers = [];
private $state;

public function attach(Observer $observer)
{
$this->observers[] = $observer;
}

public function detach(Observer $observer)
{
$index = array_search($observer, $this->observers);
if ($index !== false) {
unset($this->observers[$index]);
}
}

public function notify()
{
foreach ($this->observers as $observer) {
$observer->update();
}
}

public function setState($state)
{
$this->state = $state;
$this->notify();
}

public function getState()
{
return $this->state;
}
}

interface Observer
{
public function update();
}

class ConcreteObserver implements Observer
{
private $state;

public function update()
{
// 拉取主题的最新状态
$subject = $this->getSubject();
$this->state = $subject->getState();

// ...
}

protected function getSubject(): Subject
{
// 获取主题的引用（实现可能因具体场景而异）
}
}

$subject = new ConcreteSubject();
$observer1 = new ConcreteObserver();
$observer2 = new ConcreteObserver();

$subject->attach($observer1);
$subject->attach($observer2);

$subject->setState("新状态"); // 通知观察者状态已更改

By adopting these design patterns, code duplication can be eliminated and the readability, maintainability and scalability of the code can be improved. They provide flexible solutions that enable developers to customize and reuse code for different scenarios.

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