CodeIgniter 4 Foundations
Minimum price
Suggested price

CodeIgniter 4 Foundations

About the Book

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 8 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. 

Table of Contents

The Primers: 


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. 


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


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


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: Blog - Part 2

We'll create a simple CRUD area to manage the blog posts we created previously. While we do this we'll focus on using the testing tools that CodeIgniter ships with to keep our project running smoothly.

Project 6: Image Search

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

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: 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. 

About the Author

Lonnie Ezell
Lonnie Ezell

Lonnie Ezell is a Springfield, Missouri-based software developer, writer and musician. He has spent much of the past 8 years as a fulltime freelance consultant, helping his clients to build some amazing web properties. He maintains several open source projects include Bonfire and SprintPHP, both built on top of the CodeIgniter PHP framework. He is served as one of the CodeIgniter Council Members, helping to usher in a new, modern version of the beloved framework. He was the lead developer on the rewrite of CodeIgniter into version 4.

In the past, he co-hosted one of the premier tabletop RPG podcasts, Dragon's Landing. He currently plays guitar, penny whistle, and sings in the pirate band, Capt'n Black's Sea Dogs. When not coding, writing, or playing music, he spends most of free time with his wife, 3 kids, and 2 cats, and a gaggle of wonderful friends. 

Table of Contents

  • Introduction
  • Primer: Model-View-Controller (MVC)
    • What is MVC?
    • Primary Class Purposes
    • Other Common Class Types
  • Primer: Namespaces
    • The Simple Version
    • Going Deeper
  • Primer: Dependency Injection
    • What is it?
    • How to do it
    • How to use it
    • Why Controllers are Exempt
  • Primer: Services
    • What Are They?
    • How to Use Them
    • When to Use Them
    • Creating Your Own
    • Extending the Core Framework
  • Project 1 - Brochure Site Take 1
    • Routes
    • Displaying Our Site
  • Project 2 - Brochure Site Take 2
    • Controllers
    • Routing to Controllers
    • Displaying our page
    • Page Cache
    • Clearing the cache
  • Project 3 - Product Catalog
    • What We’re Building
    • Connecting to the Database
    • Creating the Schema
    • Building Your Model
    • Setting Up The Controller
    • Displaying the Results
    • Seeding Some Demo Data
  • Project 4 - A Simple Blog Engine
    • What we’re building
    • Database Setup
    • View Layouts
    • The Controller
    • The Routes
    • Viewing A Single Post
    • Recent Posts View Cell
  • Project 4 - A Simple Blog Engine Part 2
    • Testing Your Application
    • Getting Setup for Testing
    • Unit Testing
    • Deleting a Post
  • Project 5 - Cat API Search
    • Your API Key
    • The Form
    • Getting the Breeds
    • Searching the API
  • Project 6 - Building an API
    • What Is REST?
    • Revising The Migrations
    • Planning the API
    • The ResponseTrait
    • Listing Posts
    • Representing a Resource
    • Retrieve a Single Post
    • Create A New Post
    • Updating Existing Posts
    • Deleting a Post
    • PUT a Featured Image
    • Throttling API Access
  • Project 7 - Creating CLI Tools
    • Common CLI Script Uses
    • What We Are Creating
    • Creating the Data Model
    • Creating the Command Skeleton
    • Importing the Products
  • Epilogue

Other books by this author

The Leanpub 60 Day 100% Happiness Guarantee

Within 60 days of purchase you can get a 100% refund on any Leanpub purchase, in two clicks.

Now, this is technically risky for us, since you'll have the book or course files either way. But we're so confident in our products and services, and in our authors and readers, that we're happy to offer a full money back guarantee for everything we sell.

You can only find out how good something is by trying it, and because of our 100% money back guarantee there's literally no risk to do so!

So, there's no reason not to click the Add to Cart button, is there?

See full terms...

80% Royalties. Earn $16 on a $20 book.

We pay 80% royalties. That's not a typo: you earn $16 on a $20 sale. If we sell 5000 non-refunded copies of your book or course for $20, you'll earn $80,000.

(Yes, some authors have already earned much more than that on Leanpub.)

In fact, authors have earnedover $13 millionwriting, publishing and selling on Leanpub.

Learn more about writing on Leanpub

Free Updates. DRM Free.

If you buy a Leanpub book, you get free updates for as long as the author updates the book! Many authors use Leanpub to publish their books in-progress, while they are writing them. All readers get free updates, regardless of when they bought the book or how much they paid (including free).

Most Leanpub books are available in PDF (for computers) and EPUB (for phones, tablets and Kindle). The formats that a book includes are shown at the top right corner of this page.

Finally, Leanpub books don't have any DRM copy-protection nonsense, so you can easily read them on any supported device.

Learn more about Leanpub's ebook formats and where to read them

Write and Publish on Leanpub

You can use Leanpub to easily write, publish and sell in-progress and completed ebooks and online courses!

Leanpub is a powerful platform for serious authors, combining a simple, elegant writing and publishing workflow with a store focused on selling in-progress ebooks.

Leanpub is a magical typewriter for authors: just write in plain text, and to publish your ebook, just click a button. (Or, if you are producing your ebook your own way, you can even upload your own PDF and/or EPUB files and then publish with one click!) It really is that easy.

Learn more about writing on Leanpub