Simple Factory Pattern Overview

The Simple Factory Pattern decouples the client code from the object instantaition logic by centralizing creation inside a dedicated factory. The client requests objects from the factory instead of instantiating them directly, which improves maintainability and extensibility.

A key limitation is that adding or modifying product types often requires updating the factory itself, which violates the Open/Closed Principle (open for extension, closed for modification).

Core Interface

<?php

namespace App\Graphics;

interface Renderable
{
    public function render(): string;
}

Concrete Implementatiosn

Circle

<?php

namespace App\Graphics;

class CircleShape implements Renderable
{
    public function render(): string
    {
        return 'Rendering a circle';
    }
}

Square

<?php

namespace App\Graphics;

class SquareShape implements Renderable
{
    public function render(): string
    {
        return 'Rendering a square';
    }
}

Rectangle

<?php

namespace App\Graphics;

class RectangleShape implements Renderable
{
    public function render(): string
    {
        return 'Rendering a rectangle';
    }
}

Factory Class

<?php

namespace App\Graphics;

class GraphicFactory
{
    public const TYPE_CIRCLE = 'circle';
    public const TYPE_SQUARE = 'square';
    public const TYPE_RECTANGLE = 'rectangle';

    public function create(string $type): ?Renderable
    {
        switch ($type) {
            case self::TYPE_CIRCLE:
                return new CircleShape();
            case self::TYPE_SQUARE:
                return new SquareShape();
            case self::TYPE_RECTANGLE:
                return new RectangleShape();
            default:
                return null;
        }
    }
}

Client Usage

<?php

require_once 'vendor/autoload.php';

use App\Graphics\GraphicFactory;

$factory = new GraphicFactory();
$shape = $factory->create(GraphicFactory::TYPE_CIRCLE);

if ($shape !== null) {
    echo $shape->render();
}