bind

Laravel's bind method tells the service container which class it should create when an interface is requested. We can understand this clearly through a payment example.

Imagine that our checkout system depends on a PaymentMethod interface. The controller does not need to know which payment provider is used. Laravel chooses the correct class through the binding.

Create the PaymentMethod Interface

First, create a contract for every payment method in the application.

<?php

namespace App\Contracts;

interface PaymentMethod
{
    public function pay(int $amount): string;
}

Every payment class must implement the pay method.

Create the Stripe Payment Method

Now create a Stripe implementation of the interface.

<?php

namespace App\Services\Payments;

use App\Contracts\PaymentMethod;

class StripePaymentMethod implements PaymentMethod
{
    public function pay(int $amount): string
    {
        return "Payment of {$amount} cents completed with Stripe.";
    }
}

StripePaymentMethod follows the rules defined by the PaymentMethod interface.

Bind PaymentMethod to StripePaymentMethod

Laravel cannot automatically know which class should be used for the PaymentMethod interface. We define that relationship with bind inside AppServiceProvider.

<?php

namespace App\Providers;

use App\Contracts\PaymentMethod;
use App\Services\Payments\StripePaymentMethod;
use Illuminate\Support\ServiceProvider;

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

This binding means: whenever the application requests PaymentMethod, create and return a new StripePaymentMethod.

Inject PaymentMethod into the Controller

The controller can now depend directly on the interface.

<?php

namespace App\Http\Controllers;

use App\Contracts\PaymentMethod;
use Illuminate\Http\JsonResponse;
use Illuminate\Http\Request;

class CheckoutController extends Controller
{
    public function __construct(
        private readonly PaymentMethod $paymentMethod,
    ) {}

    public function store(Request $request): JsonResponse
    {
        $message = $this->paymentMethod->pay(
            amount: (int) $request->integer('amount'),
        );

        return response()->json([
            'message' => $message,
        ]);
    }
}

When Laravel creates CheckoutController, it sees the PaymentMethod dependency. It checks the binding and injects a new StripePaymentMethod object.

The flow is:

CheckoutController
        ↓ requests
PaymentMethod
        ↓ bind resolves
StripePaymentMethod

The controller only knows the PaymentMethod contract. The relationship between the interface and the Stripe class is managed by Laravel's bind method.