CODESAMPLE

Adapter - PHP

Adapter PHP

The Adapter pattern converts the interface of a class into another interface clients expect. This allows classes with incompatible interfaces to collaborate. Here, we adapt a legacy LegacyRectangle class (providing area calculation in a specific, older format) to the Shape interface (a more modern, consistent interface). The RectangleAdapter implements the Shape interface but internally uses the LegacyRectangle to provide the functionality. This implementation uses PHP’s interface system for clear contracts and dependency injection, which aligns with common PHP practices for loose coupling and testability.

<?php

// The target interface - what the client expects
interface Shape
{
    public function getArea(): float;
}

// The legacy class with an incompatible interface
class LegacyRectangle
{
    public function __construct(private float $width, private float $height) {}

    public function calculateArea(): float
    {
        return $this->width * $this->height;
    }
}

// The adapter
class RectangleAdapter implements Shape
{
    public function __construct(private LegacyRectangle $legacyRectangle) {}

    public function getArea(): float
    {
        return $this->legacyRectangle->calculateArea();
    }
}

// Client code
class AreaCalculator
{
    public function __construct(Shape $shape) {
        $this->shape = $shape;
    }

    public function calculate(): float {
        return $this->shape->getArea();
    }
}

// Usage
$legacyRectangle = new LegacyRectangle(5, 10);
$adapter = new RectangleAdapter($legacyRectangle);

$calculator = new AreaCalculator($adapter);
echo "Area: " . $calculator->calculate() . PHP_EOL;