Learn SLIM with Real Code Examples

Slim is a micro-framework that provides just the essentials for routing, middleware, and request/response handling.

It follows PSR-7, PSR-15, and PSR-17 standards for HTTP message interfaces and middleware interoperability.

Includes routing, dependency injection, error handling, and middleware support out of the box.

Ideal for building RESTful APIs, single-page applications (SPA) backends, and small-to-medium web apps.

Its simplicity allows full customization and integration with other components or frameworks.

Minimalist architecture with focus on HTTP handling

Flexible routing with route placeholders and named routes

Middleware stack for request/response modification

Integration with any templating engine or ORM

PSR-compliant HTTP messages and middleware interoperability

App - the main Slim application instance

Route - defines a path and the callback/action

Middleware - intercepts request/response for pre/post-processing

Request - encapsulates HTTP request data

Response - encapsulates HTTP response data

public/ - web server entry point

src/ - application code (Controllers, Services, Middleware)

config/ - configuration files

logs/ - error and access logs

vendor/ - Composer dependencies

Define routes with their callbacks or controllers

Apply middleware for authentication, logging, or caching

Inject dependencies via container or directly

Handle HTTP requests and generate responses

Test API endpoints or web pages

Beginner: simple REST API with a few routes

Intermediate: SPA backend with middleware authentication

Advanced: microservice architecture with multiple services

Expert: custom middleware, dependency injection, and modular apps

Architect: integrating Slim with other frameworks or legacy systems

Slim vs Laravel - micro vs full-stack

Slim vs Symfony - lightweight vs enterprise features

Slim vs Lumen - minimalism vs Laravel micro-framework

Slim vs CodeIgniter - routing-focused vs lightweight full MVC

Slim vs Zend Expressive - PSR middleware-centric frameworks

2010 - Initial Slim release by Josh Lockhart

2011 - Slim 2.x with improved routing and middleware support

2015 - Slim 3.x, fully PSR-7 compliant, middleware stack introduced

2019 - Slim 4.x, fully decoupled core, DI container support

2025 - Slim 5.x, enhanced PSR compliance, performance improvements

App - main Slim application instance

Route - maps URI paths to callbacks

Middleware - modifies request/response

Request - HTTP request object

Response - HTTP response object