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PHP interfaces how to use them and Laravel interface binding simply explained

What is a PHP Interface?

An interface in PHP is a blueprint for classes. It defines a contract that any implementing class must adhere to, specifying methods that must be implemented but not providing the method bodies. Interfaces ensure a consistent structure across different classes and enable polymorphism by allowing multiple classes to be treated through a common interface. You can read more about it here

Use without binding

Let's first talk about how to use interfaces without binding in laravel.

1.Define an Interface:

Create an interface in the App\Contracts directory.

// app/Contracts/PaymentGatewayInterface.php namespace App\Contracts; interface PaymentGatewayInterface { public function charge($amount); }
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2.Implement the Interface with Additional Methods:

// app/Services/StripePaymentGateway.php namespace App\Services; use App\Contracts\PaymentGatewayInterface; class StripePaymentGateway implements PaymentGatewayInterface { public function charge($amount) { // Logic to charge using Stripe return "Charged {$amount} using Stripe"; } }
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3.Inject the Implementation Manually:
When you instantiate the controller or the class that requires the interface, manually provide the implementation.

// app/Http/Controllers/PaymentController.php namespace App\Http\Controllers; use App\Contracts\PaymentGatewayInterface; use App\Services\StripePaymentGateway; class PaymentController extends Controller { protected $paymentGateway; public function __construct(PaymentGatewayInterface $paymentGateway) { $this->paymentGateway = $paymentGateway; } public function charge($amount) { return $this->paymentGateway->charge($amount); } }
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// routes/web.php use App\Http\Controllers\PaymentController; use App\Services\StripePaymentGateway; Route::get('/charge/{amount}', function ($amount) { $paymentGateway = new StripePaymentGateway(); $controller = new PaymentController($paymentGateway); return $controller->charge($amount); });
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Example with binding and benefits of the approach

Laravel's service container can automatically resolve dependencies for you, reducing boilerplate code. Check this example.

// app/Providers/AppServiceProvider.php namespace App\Providers; use Illuminate\Support\ServiceProvider; use App\Contracts\PaymentGatewayInterface; use App\Services\StripePaymentGateway; class AppServiceProvider extends ServiceProvider { public function register() { $this->app->bind(PaymentGatewayInterface::class, StripePaymentGateway::class); } public function boot() { // } }
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// app/Http/Controllers/PaymentController.php namespace App\Http\Controllers; use App\Contracts\PaymentGatewayInterface; use App\Services\StripePaymentGateway; class PaymentController extends Controller { protected $paymentGateway; public function __construct(PaymentGatewayInterface $paymentGateway) { $this->paymentGateway = $paymentGateway; } public function charge($amount) { return $this->paymentGateway->charge($amount); } }
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With this binding in place, you don't need to manually instantiate StripePaymentGateway. So this code is enough inside routes.

// routes/web.php use App\Http\Controllers\PaymentController; Route::get('/charge/{amount}', [PaymentController::class, 'charge']);
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In this example we have used service binding in Laravel. Service binding is used to register a concrete implementation for a given interface or abstract class in Laravel's service container. This allows Laravel to automatically resolve dependencies and inject the appropriate implementations when needed.

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