CODESAMPLE

Bridge - PHP

Bridge PHP

The Bridge pattern is a structural design pattern that lets you split an abstraction from its implementation so that objects can have different implementations. This is useful when you want to avoid a tight coupling between abstract and concrete classes, allowing you to change implementations independently without affecting the abstraction.

The code demonstrates a Shape abstraction and concrete abstractions like Circle and Rectangle. These rely on an Color interface implemented by RedColor and BlueColor. A shape’s color isn’t tied to its type; you can have a red circle or a blue rectangle. This decoupling is achieved by the Shape classes holding an instance of the Color interface. This approach is idiomatic PHP as it leverages interfaces for loose coupling and allows for flexible composition over inheritance.

<?php

// Color Interface (Implementation)
interface Color
{
    public function applyColor(): string;
}

// Concrete Implementations of Color
class RedColor implements Color
{
    public function applyColor(): string
    {
        return "Applying Red Color.";
    }
}

class BlueColor implements Color
{
    public function applyColor(): string
    {
        return "Applying Blue Color.";
    }
}

// Shape Abstraction
interface Shape
{
    public function draw(): string;
}

// Concrete Implementations of Shape
class Circle implements Shape
{
    protected Color $color;

    public function __construct(Color $color)
    {
        $this->color = $color;
    }

    public function draw(): string
    {
        return "Drawing a Circle " . $this->color->applyColor();
    }
}

class Rectangle implements Shape
{
    protected Color $color;

    public function __construct(Color $color)
    {
        $this->color = $color;
    }

    public function draw(): string
    {
        return "Drawing a Rectangle " . $this->color->applyColor();
    }
}

// Client Code
$redCircle = new Circle(new RedColor());
$blueRectangle = new Rectangle(new BlueColor());

echo $redCircle->draw() . PHP_EOL;
echo $blueRectangle->draw() . PHP_EOL;

?>