Lifecycle of a Laravel request: Explained with examples

Introduction

The framework Laravel has simplified the development of PHP web applications with its elegant syntax and comprehensive system for handling web requests. In this tutorial, you will get a deep dive into the request lifecycle of a Laravel application, with various examples that illustrate how a request travels through the server and finally renders a response on the client’s browser.

Laravel packs a complex series of actions into a particularly high-level and straightforward interface that, while making development more accessible, can pose some questions about what’s going on under the hood. Understanding this process clarifies how Laravel works, making you a more effective developer when it comes to building, optimizing, and debugging your applications.

The Lifecycle Overview

Every Laravel request follows a predefined path before rendering a response. This begins when a request hits the server and ends with the application returning a response back to the user. The main stages of the request lifecycle include:

1. The entry point into the application via public index.php file.
2. Request handled by HTTP/Console kernel.
3. Bootstrapping and service provider registration.
4. Dispatching the request to listen to routes.
5. Executing controller logic and middleware.
6. Rendering and returning the response.

This sequence ensures that the application is thoroughly prepared to handle every aspect of the request.

The Role of the index.php File

<?php

// Laravel public/index.php

require __DIR__.'/../vendor/autoload.php';
$app = require_once __DIR__.'/../bootstrap/app.php';

$kernel = $app->make(Illuminate\Contracts\Http\Kernel::class);

$response = $kernel->handle(
    $request = Illuminate\Http\Request::capture()
);

$response->send();
$kernel->terminate($request, $response);

The index.php file is the frontend controller and standard entry point for all requests entering a Laravel program. This script bootstraps the framework, initializing the core components necessary for the application to run.

Kernel’s Role in the Request Lifecycle

// bootstrap/app.php

$kernel = $app->make(Illuminate\Contracts\Http\Kernel::class);

$response = $kernel->handle(
    $request = Illuminate\Http\Request::capture()
);

Both the HTTP and Console Kernels are central to the request lifecycle. They handle the request by first invoking middleware for pre-request processing and later sending the $request object through to the application.

Service Providers and Bootstrapping

<?php

// part of the bootstrapping process

$app->register(App\Providers\RouteServiceProvider::class);

The bootstrapping context elaborates on how quickly service providers should load when needed, defining the core services that the Laravel application depends on, such as logging, events, and routing.

The Routing Layer

<?php

// routes/web.php

Route::get('/', function () {
 return 'Hello, world!';
});

Routes in Laravel define endpoints and associate them with controller actions. The routing component interprets the URI requested and executes the associated closure or controller method.

Controllers and Middleware

<?php

// app/Http/Controllers/HelloWorldController.php

namespace App\Http\Controllers;

use Illuminate\Http\Request;

class HelloWorldController extends Controller
{
 public function show(Request $request)
 {
 // ...
 }
}

<?php

// app/Http/Middleware/Authenticate.php

namespace App\Http\Middleware;

use Closure;

Class Authenticate
{
 public function handle($request, Closure $next)
 {
 // Authentication logic
 return $next($request);
 }
}

Middleware are filters that execute around a request in Laravel. Controllers then handle the incoming request, perform actions and return responses.

Generating the Response

// Generate a response using a view
return view('greetings.hello');

Once the controller finishes, the final step for the Laravel request lifecycle involves compiling the returned data and creating an HTTP response that is sent back to the user’s browser.

Conclusion

In this tutorial, you explored the anatomy of a Laravel request. By understanding these processes, you’re much better equipped to diagnose issues, optimize performance, create middleware, and generally take advantage of what the framework has to offer.