This book is under active development. New chapters are completed regularly. If you find any errors, please let me know and I will get them fixed up as soon as possible.

Learn how to get the most out of CodeIgniter 4 from the lead developer on the project. 

CodeIgniter is typically seen as an old framework that doesn't work well with modern development practices. In version 4, it has been completely rewritten from the ground up to modernize it, while still keeping many of the same hallmarks of the framework: simplicity, speed, and flexibility. This brings with it a lot of new concepts and new tools that you need to get to speed with. 

CodeIgniter 4 Foundations is here to help you do just that. It first dives into some of the essential new concepts that you need to be familiar with, why they're important, and illuminates some of the behind-the-scenes decision making that brought the framework to its current state. Next, we'll step through 9 small projects, each designed to highlight new features of the framework, and each building on the one before it. Every project comes with the full application code-base for you to examine and use in your own projects. 

Planned Table of Contents

The Primers: 

Namespaces

Intended for users of previous versions of CodeIgniter, or newer PHP developers, this chapter helps you understand namespaces, why they're important, and how they're used in CodeIgniter. Getting a handle on namespaces will unlock the real flexibility that CodeIgniter gives you.

Dependency Injection

This is a crucial topic, often clouded in many layers of other best practices, but is really simple to understand. You'll learn what it is, why it's important, and how you can use it in your projects to keep them as maintainable and testable as possible. 

Services

Closely related to Dependency Injection, you'll become familiar with what Services are in CodeIgniter, how to use existing ones, create new ones, and when you should consider it - and when you shouldn't.

Getting Started

Requirements

This chapter covers what the requirements for the latest version of the framework all, and which optional ones you should consider.

Installation

Covers two different methods to install CodeIgniter and get it running locally so that you can get started developing on it. Covers Apache and NGINX usage, as well as using PHP's built-in server to get started as quick as possible. 

Application Structure

Along with the code rewrite, changes have been made to the codebase as well. This chapters gets veteran and new users alike grasping where everything is stored, what directories should be writable, and which should be hidden. It also explores how you can (and should!) modify the application directory to your project's needs. 

The Projects

Project 1: Brochure Site - Take 1

This project creates a very simple brochure-type of website, getting you familiar with the request/response flow, basic routing, routing with closures, and displaying simple views. While some of the techniques described here won't be used much in larger sites, it provides a quick way to get started and seeing progress fast. And these techniques can be great for very simple sites like this brochure site, or for rapidly prototyping a site. 

Project 2: Brochure Site - Take 2

This time we redo the previous site into something much more representative of how you would work on larger projects. 

Project 3: Product Catalog

E-commerce is a huge portion of the web. While this project will not cover all of the details by any stretch of the imagination, it will tackle creating a simple front-end to display the products. Along the way, you'll learn the basic usage of Models, a simple way of creating site-wide templates, how to use "magic" routing, and learn how simple pagination is. 

Project 4: Blog

Next, we'll create a super-simple blog engine. We'll look at using Entities/Repositories as a different way to work with data. You'll explore View Cells that help separate out the logic for most popular posts. We'll explore using database Migrations to version your database, and Seeds to fill it with sample data using Faker. 

Project 5: Flickr Search

In this project, we'll create a simple, single page, AJAX-based search engine for Flickr. This shows how to use the built-in HTTP client to access third-party API's, how to use the cache engine, and how simple it can be to use a full-page cache for the ultimate performance boost. 

Project 6: Drip Mailer

A common need for marketing, this project dives into creating cronjobs and queues to email marketing letters on a scheduled.

Project 7: A Simple API

Next, we'll tackle creating a very simple REST-ful API, able to output it's data in either JSON or XML using Content Negotiation, that uses the provided API Response trait to give consistent - and simple - API responses for many of the most common requirements. You'll also create Filters to do very simple authentication checks and rate throttling. 

Project 8: Rigging up an Admin Area

This project brings in Composer to the mix, using the robust Sentry for auth needs. We'll get it working with CodeIgniter's new database layer. Finally, we'll explore how to keep our code in a modular format to easily share the Admin space. 

Project 9: Creating CLI Commands

The final project is a little different. Instead of creating some site or app, you'll be working the command-line tools to create custom code generation methods you can tweak for your development needs.