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

Claudio Ctin4 months ago4 mins

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 AppContracts directory.

// app/Contracts/PaymentGatewayInterface.php
namespace AppContracts;

interface PaymentGatewayInterface {
public function charge($amount);
}

2.Implement the Interface with Additional Methods:

// app/Services/StripePaymentGateway.php
namespace AppServices;

use AppContractsPaymentGatewayInterface;

class StripePaymentGateway implements PaymentGatewayInterface {
public function charge($amount) {
// Logic to charge using Stripe
return “Charged {$amount} using Stripe”;
}
}

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 AppHttpControllers;

use AppContractsPaymentGatewayInterface;
use AppServicesStripePaymentGateway;

class PaymentController extends Controller {
protected $paymentGateway;

public function __construct(PaymentGatewayInterface $paymentGateway) {
$this->paymentGateway = $paymentGateway;
}

public function charge($amount) {
return $this->paymentGateway->charge($amount);
}
}

// routes/web.php
use AppHttpControllersPaymentController;
use AppServicesStripePaymentGateway;

Route::get(‘/charge/{amount}’, function ($amount) {
$paymentGateway = new StripePaymentGateway();
$controller = new PaymentController($paymentGateway);
return $controller->charge($amount);
});

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 AppProviders;

use IlluminateSupportServiceProvider;
use AppContractsPaymentGatewayInterface;
use AppServicesStripePaymentGateway;

class AppServiceProvider extends ServiceProvider {
public function register() {
$this->app->bind(PaymentGatewayInterface::class, StripePaymentGateway::class);
}

public function boot() {
//
}
}

// app/Http/Controllers/PaymentController.php
namespace AppHttpControllers;

use AppContractsPaymentGatewayInterface;
use AppServicesStripePaymentGateway;

class PaymentController extends Controller {
protected $paymentGateway;

public function __construct(PaymentGatewayInterface $paymentGateway) {
$this->paymentGateway = $paymentGateway;
}

public function charge($amount) {
return $this->paymentGateway->charge($amount);
}
}

With this binding in place, you don’t need to manually instantiate StripePaymentGateway. So this code is enough inside routes.

// routes/web.php
use AppHttpControllersPaymentController;

Route::get(‘/charge/{amount}’, [PaymentController::class, ‘charge’]);

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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