<?php
namespace AppProviders;

use IlluminateSupportServiceProvider;
use AppServicesPaymentGatewayInterface;
use AppServicesStripePaymentGateway;

class PaymentServiceProvider extends ServiceProvider
{
    public function register(): void
    {
        // Bind Interface to Concrete Implementation as a Singleton
        $this->app->singleton(PaymentGatewayInterface::class, function ($app) {
            return new StripePaymentGateway(
                apiKey: config('services.stripe.secret'),
                currency: 'USD'
            );
        });
    }
}

<?php
namespace AppHttpRequests;

use IlluminateFoundationHttpFormRequest;
use IlluminateValidationRule;

class StoreOrderRequest extends FormRequest
{
    public function authorize(): bool
    {
        return $this->user()->can('create', Order::class);
    }

    public function rules(): array
    {
        return [
            'item_id'  => ['required', 'integer', 'exists:items,id'],
            'quantity' => ['required', 'integer', 'min:1', 'max:100'],
            'coupon'   => ['nullable', 'string', 'exists:coupons,code'],
        ];
    }
}

// Eager Loading Relationships (2 SQL queries instead of 101!)
$orders = Order::query()
    ->with(['customer:id,name,email', 'items.product'])
    ->where('status', 'COMPLETED')
    ->latest()
    ->paginate(25);

// Distributed Atomic Lock in Redis (Prevents financial double-charge race conditions!)
use IlluminateSupportFacadesCache;

$lock = Cache::lock('process_charge_user_' . $user->id, 10);

if ($lock->get()) {
    try {
        $paymentGateway->charge($user, $amount);
    } finally {
        $lock->release();
    }
} else {
    throw new RuntimeException('Concurrent transaction in progress, please retry');
}