How to use the Proxy design pattern in PHP for lazy loading and caching?

@daisha 

The Proxy design pattern is a structural pattern that allows for the creation of a placeholder object that can defer the loading of the actual object until it is actually needed. This can be useful in situations where loading the actual object is expensive or time-consuming, and can improve performance by deferring its creation until it is actually needed.

In PHP, the Proxy design pattern can be used for lazy loading and caching of objects. Here is an example of how to implement it:

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interface Subject {
    public function request(): void;
}

class RealSubject implements Subject {
    public function request(): void {
        echo "RealSubject: Handling request.
";
    }
}

class Proxy implements Subject {
    private $realSubject;

    public function request(): void {
        if (!$this->realSubject) {
            $this->realSubject = new RealSubject();
        }
        $this->realSubject->request();
    }
}

// Usage example
function clientCode(Subject $subject) {
    // ...

    $subject->request();

    // ...
}

echo "Client: Executing the client code with a real subject:
";
$realSubject = new RealSubject();
clientCode($realSubject);

echo "
";

echo "Client: Executing the same client code with a proxy:
";
$proxy = new Proxy();
clientCode($proxy);

In this example, we have an interface Subject that defines the request() method. We also have a RealSubject class that implements the Subject interface, and a Proxy class that also implements the Subject interface.

The Proxy class maintains a reference to a RealSubject object, but only creates it when the request() method is called for the first time. Subsequent calls to the request() method simply delegate to the RealSubject object.

This pattern can also be used for caching. For example, the Proxy class could maintain a cache of previously loaded objects, and return them instead of creating new ones.

Note that this is just a basic example, and there are many variations of the Proxy pattern that can be used depending on the specific requirements of your application.