Slim Framework Tutorial

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Slim is a PHP micro-framework — a small, focused toolkit for building web applications and APIs quickly, without the weight of a full-stack framework like Laravel or Symfony. It gives you routing, middleware, and request/response handling, and gets out of your way otherwise.

Where this fits: Everything you learned in Core PHP — variables, arrays, OOP, PDO, sessions — still applies here. Slim doesn't replace PHP; it just organizes how your PHP code handles incoming web requests.

Micro-Framework vs Full-Stack Framework

	Micro-framework (Slim)	Full-stack (Laravel, Symfony)
Comes with	Routing, middleware, PSR-7 request/response	ORM, templating, auth, mail, queues, and more — all built in
Best for	APIs, small apps, microservices, learning the underlying concepts	Large applications that need everything out of the box
Learning curve	Small — a handful of core concepts	Larger — many conventions to learn

A Quick Look Ahead

Example: A Complete Slim App in a Few Lines

<?php
require __DIR__ . '/../vendor/autoload.php';

$app = \Slim\Factory\AppFactory::create();

// Define a route
$app->get('/hello/{name}', function ($request, $response, $args) {
    $response->getBody()->write("Hello, " . $args['name'];
    return $response;
});

$app->run();

Note: This code is a correct, real Slim example — but this website itself doesn't run Composer/Slim, so you won't see it executed live on this page. Copy it into your own Slim project (after installing Slim via Composer on the next page) to actually run it.

Why Learn Slim?

Reason	What it means for you
Great for APIs	Minimal overhead, perfect for JSON REST APIs and microservices
PSR standards	Built on PSR-7 (HTTP messages) and PSR-11 (containers) — skills that transfer to other frameworks
Easy to understand	Small codebase means you can actually read how it works under the hood
Composer-based	A great first project to practice modern PHP dependency management

Next steps: Head to Installation & Setup to install Slim via Composer and see the project structure.

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