The Definitive Guide to CodeIgniter 4: From Zero to Expert in PHP Web Development

In today's PHP web development landscape, CodeIgniter 4 remains a solid and efficient choice for building robust applications. This modern framework is characterized by its lightness, an accessible learning curve, and exceptional performance, making it an excellent gateway to development with PHP frameworks. For the experienced developer, it offers the flexibility and tools needed for medium and large-scale projects. This SUPER pillar post is your definitive resource, designed to take you from the most basic concepts to the most advanced implementations.

Throughout this extensive post, I will provide a route to our more detailed publications on CodeIgniter 4. We will cover installation, MVC architecture, database interaction, creating RESTful APIs, and many other essential tasks. Our goal is to provide you with a complete roadmap, full of code snippets, technical explanations, and practical advice.

Get ready to master CodeIgniter 4 and build high-performance web applications.

When to Use CodeIgniter 4?

Here's a point I consider very interesting to address, and that is when to use CodeIgniter if we compare it with other PHP frameworks, that is, from the same environment. If we compare it with Laravel, I believe it has absolutely nothing to do, let's be clear.

For example, if you want to create a REST API to connect it to another application, obviously Laravel will give you many more options, such as authentication, handling via SPA or directly by tokens. CodeIgniter also has its own, but obviously Laravel has many more features. With this, integration is easier, cleaner, and therefore more maintainable. That is, everything is excellent, besides having another huge ecosystem to work with, and in this case CodeIgniter pales greatly.

Who is this type of framework for?

You might ask: what is this type of framework for? Another very important point is that the update curve we have in frameworks like C4 is not as high as the one we have in Laravel, where we find practically daily or weekly updates, with new functionalities and bug fixes. In contrast, CodeIgniter has a much slower update curve, where most are bug fixes and not so much adding functionalities.

But, however it may be, this scenario can be excellent for a certain audience. That is, not all people are programmers who want to be constantly receiving that enormous flow of updates we have in Laravel. There are those who prefer something more stable, and in such cases, CodeIgniter can be an excellent option.

Again, I believe this framework can adapt very well to an audience that wants to develop simple web applications: blogs, online stores, etc. Note that you could even grow this quite a bit with CodeIgniter, but they don't want to be tied to that update curve that sometimes becomes quite complex, as happens with Laravel.

A comparison to understand it better

I see it a bit like this so that my point is better understood:
when you compare a casual video game player, who plays very occasionally —half an hour a day or a couple of hours a week— with an enthusiastic player, who plays at least 3 to 5 hours a day.

That is exactly the type of audience or the example I want to give you:

Laravel is the enthusiastic player who plays several hours a day.

CodeIgniter is the casual player, who simply wants to play a few hours a week, or a few minutes a day.

And that's perfectly fine, as not everyone wants to be tied to or keep pace with the enormous updates that Laravel offers. There are those who simply want something a little more stable, that they know will work in practically any PHP environment in which they want to place it, which we cannot always say about Laravel.

Why Learn to Develop with CodeIgniter 4

The world of web development is constantly evolving, and every day new tools and technologies emerge, in addition to existing ones changing. Frameworks like Laravel, which are more versatile but also have a steeper learning curve, others like Django or similar, or Go, are excellent, but they also have a high learning curve, with a more specific audience, and these should be an "after" learning the basics of web technologies.

If you are reading this article, it is because you are new to the world of programming and want to take the first steps in web development. Surely you already have at least some basics in web development with HTML, CSS, and JavaScript, but you want to see data stored persistently, you want to add logic to your pages, you probably have an idea to develop a web project like a blog, online store, or something similar and you want to create something of your own to gradually extend, and the CodeIgniter framework is for you.

CodeIgniter is ideal for taking the first steps and beyond

I experienced all of this as I am narrating it. I started creating this very blog with CodeIgniter in its version 2 and maintained it for many years. Little by little, I extended the app until it became what it is now, which, yes, is not an immensely large app and has several aspects to improve, but it is mine. I was able to see it evolve and it continues to evolve.

And that is because CodeIgniter is excellent at this, for creating your first apps, being able to advance without as many detours as other frameworks have, and best of all, PHP is widely supported.

The problems you may encounter with non-PHP technologies is that they have a more specific audience. If you search for web servers, you will see that, if not all, the vast majority use PHP, with the trilogy of Apache, MySQL, and of course PHP, ready to make our projects economically. And this is where PHP and your desire to learn it come into all of this; it is for people like you who want to start their small projects, and here you already have a niche or possible business that you can grow, where many people have an idea but do not know how to carry them out, and YOU, who know how to program and want to learn to create these first apps, already have everything served.

Even if other frameworks are more powerful or have more options, they are not for everyone or not for small or medium projects, which is where frameworks like CodeIgniter truly shine and are ideal for these projects, and therefore a great candidate for beginners to learn to develop.

First steps in web development with CodeIgniter

Without a doubt, choosing CodeIgniter as the first framework to develop with was one of the best decisions I have made in my life, and one that can be used as a basis to learn other frameworks and learn in an organized and efficient way, and which can also serve you. By having a simple structure, being conservative in code, widely scalable and programmable with a low learning curve, do not hesitate to develop with this technology.

What is CodeIgniter?

CodeIgniter is an open-source web framework for PHP that allows you to create dynamic and scalable web applications quickly and efficiently; we can create all types of applications, from large-scale to small. It is a framework with a long time in the market, with slow but sustained development, and they do not maintain a version of the framework for many years, meaning that by learning it, we will not have radical changes for a good period of time.

Advantages of CodeIgniter

Ease of Learning:
- As we mentioned earlier, CodeIgniter is known for its smooth or gentle learning curve. Its simple syntax and logical structure make it easy to understand and implement projects.
Performance:
- CodeIgniter is lightweight and fast. Its MVC (Model-View-Controller) architecture allows for efficient processing and quick server response. Many other frameworks have a variant of MVC, so why not learn it well from this framework.
Abundant Documentation:
- CodeIgniter has extensive official documentation and an active community. This facilitates problem-solving and access to useful resources. For my part, on this blog, you will find a large number of resources; I also have a course and book on this technology that will help you go from 0 to 100 in CodeIgniter in a very simple way.
Integrated Security:
- CodeIgniter includes built-in security features, such as protection against XSS (Cross-Site Scripting) and CSRF (Cross-Site Request Forgery) attacks. It also has a module called Shield for authentication and permissions, which is great and easy to use and implement. With this, you can develop all types of applications that are not necessarily small, as CodeIgniter allows development for projects of all types and sizes.
Flexibility:
- CodeIgniter does not impose a rigid structure. You can adapt it according to your specific needs and take advantage of its libraries and helpers. Although we do not have many libraries for CodeIgniter, we have those of PHP that are easily included and adapted in this framework.
Database Compatibility:
- CodeIgniter is compatible with multiple database management systems, such as MySQL, PostgreSQL, and SQLite. All web frameworks use databases and have an ORM; in CodeIgniter, you can also use this structure.

Ideal Scenarios for CodeIgniter

Small and Medium Projects:
- CodeIgniter is ideal for small to medium-sized web projects. Its agility and performance make it perfect for fast and efficient applications.
Rapid Prototype Development:
- If you need to create rapid prototypes or MVPs (Minimum Viable Products), CodeIgniter allows you to develop basic functionalities in a short time.
Business Applications:
- CodeIgniter is an excellent option for internal business applications or management systems.

As you can appreciate, CodeIgniter allows the development of all types of projects, and as I mentioned before, all frameworks have more similarities than differences. Once you master CodeIgniter, you can continue to scale to other technologies, but that will be the subject of another article.

How long does it take to learn CodeIgniter?

If you already know how to program in PHP and obviously web technologies, learning CodeIgniter will be very easy. CodeIgniter, as we mentioned before, has a fairly low learning curve compared to other web frameworks. The most complicated thing might be MVC, which if you have never used this pattern, it can initially be a bit difficult to understand, but it is essential since many modern technologies use the same or variants of MVC.

So, you can learn to work with CodeIgniter in a basic way in a few days. First, you must learn the folder structure, then the controllers with the routes, and from this point, the views, then learn its ORM, and with this, you have the very basics in CodeIgniter and little by little you can continue extending to the rest of the modules.

Remember that this platform is the most complete you will find to learn CodeIgniter.

What should I know before working with CodeIgniter?

As we mentioned before, you must learn to work with PHP, and logically, the technologies involved in this such as HTML, CSS, and JavaScript, the usual trilogy. It is true that one thing is client technology and another is server technology, like PHP, but even so, both sides work together, and to work on views you will need to know HTML, and if you don't want to have horrible pages, you will have to learn CSS. JavaScript could be the most optional of these technologies, but it is still always good to know JavaScript since it is always present in web development in some way.

Why learn CodeIgniter? or Is it worth learning CodeIgniter? What skills should I have?

To summarize a bit, yes, it is worth learning CodeIgniter if you are a new developer. If you already know more complete frameworks, it will be extremely easy to start with CodeIgniter and thus master another technology, and if you don't know any web framework technologies, CodeIgniter can be a great entry point for you to create your first projects and get your first jobs, since PHP is on most servers today and CodeIgniter has support for all of them by having very modest requirements if we compare them against the almighty Laravel.

CodeIgniter is a fast and agile framework, weighing a few MB and easy to learn. It is a technology, PHP is still a demanded technology today, but programming in pure PHP is very complicated since everything gets disorganized very easily, bringing the known problems such as scaling problems, modularization, and in summary, a total disaster and waste of time, but all this is solved by using a framework like Django.

As we mentioned before, you must know PHP and its basics to get started. I would also recommend that you understand at least theoretically MVC since this is the heart of modular and, therefore, scalable and professional applications.

Chapter 1: Installation and Setup of Your CodeIgniter 4 Project

The first step for any developer is to establish a functional working environment. CodeIgniter 4 has simplified this process, allowing for quick setup in both local and production environments.

1.1. Requirements and Installation Methods: Manual vs. Composer

CodeIgniter 4 is a modern PHP framework characterized by being easy to use, with a better learning curve than other frameworks, few requirements, easy to configure and install. It is an agile framework that provides a large number of features and functionalities, following modern schemes and patterns. It is scalable because it uses Composer, allowing easy installation of new dependencies and keeping the project up to date.

The current version of CodeIgniter 4 requires PHP 8.2 or higher to function. Although you can install it manually by downloading the framework from its official site and unzipping it on your web server, the most recommended way to work with CodeIgniter 4 is through Composer.

Composer is the package management system for PHP that facilitates the installation, updating, and management of libraries and dependencies. To create a new CodeIgniter 4 project with Composer, simply run:

$ composer create-project codeigniter4/appstarter project-root

Where project-root will be the name of your application. This method ensures that your project is up to date and will allow you to easily add new functionalities through external packages. Manual installation is advisable only for quick tests or to understand its basic structure, but for serious development, Composer is indispensable, as detailed in our article on the installation of CodeIgniter 4.

1.2. Recommended Development Environments

Having an optimized local development environment is crucial. Depending on your operating system, you have several options:

Windows and macOS: We highly recommend Laravel Herd. Although its name suggests Laravel, being a complete PHP environment, it works perfectly with CodeIgniter. It offers quick setup and manages PHP, Nginx, and your databases with ease. If you prefer something more traditional on Windows, you can use WAMPP or XAMPP, installing Composer separately and manually configuring your Virtual Hosts.
Linux: On Linux, the most common option is to manually install a LAMP (Linux, Apache, MySQL, PHP) or LEMP (Linux, Nginx, MySQL, PHP) stack, as Laravel Herd is not available for this operating system.

For database management, on macOS and Windows, tools like DBngin (https://dbngin.com/) allow you to manage MySQL, PostgreSQL, and other databases visually and simply. If you work with macOS and want a more modular approach, you can use Homebrew to install PHP and MySQL independently, taking advantage of Apache already being installed by default.

1.3. Serving Your First Application: Running CodeIgniter

Once installed, there are several ways to run your CodeIgniter 4 application and view it in the browser:

With Built-in Server (Spark): The most direct and recommended way for development is to use CodeIgniter's built-in server, through its Spark command line:
```
$ php spark serve
```
This will start a development server at http://localhost:8080/, without the need to configure Apache or Nginx.
With Web Server (Apache/Nginx): If you are using an environment like Laragon or Laravel Herd on Windows, a clean URL (e.g., http://yourproject.test) will automatically be generated via Virtual Hosts. If you don't use these tools or are on Linux, you will need to manually configure a Virtual Host in Apache or Nginx that points to your project's public directory.

You can delve deeper into execution options in our article on how to run the application in CodeIgniter 4 in a browser.

1.4. The Structure of a CodeIgniter 4 Project

CodeIgniter 4 organizes your code logically to facilitate maintainability. Key folders are:

app/: This is where all your application code resides (Controllers, Models, Views, Configurations, etc.). It's where you'll spend most of your time.
system/: Contains the framework's core. Files here should never be modified; your customizations should go in app/.
public/: The only folder accessible from the browser. It contains the index.php file (the entry point) and your public assets (CSS, JS, images).
writable/: Contains files that the framework needs to write, such as logs, cache, or user uploads, keeping the rest of the project without write permissions for greater security.
tests/: This is where your automated tests are stored.

For a detailed description of each folder and its purpose, consult our guide on the organization of a CodeIgniter 4 project.

1.5. Enabling Developer Mode and the .env File

The .env file (a renamed copy of env) is crucial for configuring your application according to the environment (development, production). To see detailed errors on screen during development, you must set the CI_ENVIRONMENT variable to development in your .env file. This is essential for efficient debugging. In production, this variable should be production so that errors are logged in writable/logs/ instead of being displayed to the user, for security reasons.

.env files are also the ideal place to store database credentials, API keys, and other configurations that vary between environments. For more details on how to enable developer mode and manage the .env.

Chapter 2: Fundamental Framework Concepts (MVC)

CodeIgniter 4 firmly adheres to the Model-View-Controller (MVC) pattern, an architecture that promotes separation of concerns and code modularity.

2.1. Controllers and Views: Your First "Hello World"

In CodeIgniter, execution begins with a Controller. By default, you have a Home controller in app/Controllers. Public functions within a controller are associated with specific routes. The index() method is executed by default when you access the root of the application. To display content to the user, controllers return Views, which are PHP files (e.g., welcome_message.php in app/Views) that are rendered as HTML. CodeIgniter 4, unlike its version 3, requires the index.php file to be inside the public folder.

To create your first function and view it, you can add a test() method to your Home controller that simply returns a string. Then, in app/Config/Routes.php, you define a GET route that points to that method. This basic process allows you to understand how controllers and views connect to display information in the browser. Consult our article "Creating our first Hello World in CodeIgniter 4" for a step-by-step guide.

2.2. Handling Routes and URLs

Route configuration in CodeIgniter 4 is a robust system that links a URI to a function within a controller. They are defined in app/Config/Routes.php. The basic parameters of a route are the URI, the controller, and the function to execute.

Route Types: You can define routes for different HTTP methods: get(), post(), put(), patch(), and delete(). Attempting to access a post route with a GET request will result in a 404 error, unless you explicitly define both routes.
Route Grouping: To organize routes with a common URI (e.g., /admin/users, /admin/products), you can group them, which improves the readability and maintainability of your routes file.
Route Parameters and Placeholders: You can pass data to your controllers through URL segments, using placeholders like (:num) for numbers, (:alpha) for alphabetic characters, or (:any) for any character.
Named Routes: Assigning a name to your routes allows you to reference them by their name in your code, making it easy to change the URL structure without having to manually update each link.
Resource CRUD: CodeIgniter offers a resource() method that automatically generates all the necessary routes for CRUD (Create, Read, Update, Delete) operations of an entity, greatly simplifying development.
AutoRoute: You can enable setAutoRoute(true) for CodeIgniter to automatically generate routes based on your controllers, although this can be less explicit and harder to debug in large projects.

All these aspects are addressed in detail in the article on "Handling Routes and URLs in CodeIgniter 4".

Chapter 3: Interacting with the Database

Data access and manipulation are the cornerstone of any dynamic application. CodeIgniter 4 provides a robust set of tools to manage your database efficiently and securely.

3.1. Models: Your Application's Data Layer

Models in CodeIgniter 4 are classes that extend CodeIgniter\Model and act as the primary interface for interacting with your database tables. Each model is typically linked to a specific table. For a model to be functional, you must define key properties such as:

$table: The name of the table associated with the model.
$primaryKey: The name of the column that is the primary key.
$allowedFields: An array of fields that are allowed to be inserted or updated through the model (fundamental for security).
$returnType: Defines whether queries return arrays or objects.
$useSoftDeletes: To implement "soft deletion" (marking records as deleted instead of physically deleting them).
$useTimestamps, $createdField, $updatedField: For automatic management of created_at and updated_at columns.

You can create models using php spark make:model ModelName. Models encapsulate business logic and provide methods for CRUD operations (Create, Read, Update, Delete), joins, wheres, pagination, and other advanced queries. In CodeIgniter 4, migrations and models are separate components, unlike other frameworks. Deepen your understanding in "Create models in CodeIgniter 4".

3.2. Migrations: Versioning Your Database Schema

Migrations are CodeIgniter 4's mechanism for managing changes to your database schema in a controlled and versioned manner. They allow you to define the creation, modification, or deletion of tables and columns in PHP files, ensuring schema consistency across different environments and collaborators.

Creation: They are generated with php spark migrate:create MigrationName.
Structure: Each migration file contains up() methods (to apply changes) and down() methods (to revert them).
Execution and Reversal: php spark migrate applies pending migrations, and php spark migrate:rollback reverts them. You can even "refresh" all migrations with php spark migrate:refresh.
Enums and Foreign Keys: Migrations also allow you to define ENUM column types or configure foreign keys (FKs) to establish relationships between tables.

Mastering migrations is crucial for collaborative development and for maintaining a clear history of changes in your database. Consult "Migrations in CodeIgniter 4" for a complete guide.

3.3. Seeders: Populating the Database with Test Data

Seeders are complements to migrations, used to programmatically generate test data. They are especially useful after performing a migration rollback, when you lose data. With seeders, you can repopulate your database with relevant data in a matter of seconds.

They are generated with php spark make:seeder SeederName and executed with php spark db:seed SeederName. Each seeder has a run() method where you define the logic for inserting data (e.g., creating test users or products). It is a recommended practice to create one seeder per entity or for groups of related data. Learn how to use them in "Seeders in CodeIgniter 4".

3.4. Deleting Records (CRUD Operations)

The Delete operation is an essential part of any CRUD. In CodeIgniter 4, it is performed through models, using the delete($id) method. It is good practice to verify the existence of the record before attempting to delete it and to handle the response appropriately (e.g., show a 404 page if the record does not exist). From the controller, once deleted, the user is usually redirected to a listing view with a success message. This process is explained in "Delete records in CodeIgniter 4".

Chapter 4: Common Tasks in Web Development with CodeIgniter 4

Beyond the fundamental structure, web development involves a series of recurring tasks that CodeIgniter 4 simplifies with its tools and abstractions.

4.1. Form Handling and Data Validation

Forms are the main bridge between the user and your application. CodeIgniter 4 provides a robust system for processing form data (GET and POST requests) and, crucially, for validating it. Validation is fundamental to ensuring data integrity and security. You can define predefined validation rules (required, minimum/maximum length, valid email, numeric, etc.) directly in your controllers or in specific configuration files (app/Config/Validation.php).

You can also create custom validation rules to adapt them to your business logic, and even pass parameters to these rules. To remember previous form values after a redirection (useful in case of validation errors), CodeIgniter offers the old() function. The complete form management, including customizing error messages and integration with Bootstrap, is detailed in "Sending GET and POST Requests (Form) in CodeIgniter 4".

4.2. Creating Listing Views and Pagination

Displaying data collections clearly and organized is a common task. CodeIgniter 4 simplifies the creation of listing views, often in table format, and offers an efficient pagination system. You can use any CSS framework like Bootstrap 5 for design.

From the controller, you can get paginated data using the paginate() method of your models, and in the view, the $pager->links() function will automatically generate the pagination links. In addition, CodeIgniter 4 facilitates the implementation of advanced search filters, allowing users to search, sort, and classify information efficiently. This process is explained in "Create a listing view or table in CodeIgniter 4 with Bootstrap 4 or 5 style".

4.3. Uploading and Digital Processing of Files and Images

The "upload" functionality or file upload is a necessity in almost any application. CodeIgniter 4 handles file uploads securely, allowing you to validate files (type, size) and move them to secure locations. The process involves verifying the request, validating the file, and moving it to a folder like writable (not directly accessible via HTTP for greater security) or public (directly accessible, but with precautions). We show you how to do it in "How to upload files or images in CodeIgniter 4".

In addition, CodeIgniter 4 offers tools for digital image processing, allowing you to perform operations such as rotating, resizing, cropping, and adjusting the quality of uploaded images. This is essential for optimizing the performance and visual aspect of your application. These operations are performed through the Config\Services::image() service and are explained in "Digital image processing in CodeIgniter 4".

4.4. Generating PDFs from HTML with Dompdf

Generating PDF documents from HTML content is a demanded functionality in many applications. CodeIgniter 4, although it does not have a native package, integrates perfectly with PHP libraries like Dompdf. Dompdf is an HTML to PDF converter that allows you to take an HTML view (generated with Blade or simply a PHP template), apply CSS styles to it, and render it as a PDF. The process is simple: you install Dompdf via Composer, pass the HTML to the library, configure the paper size, and finally render and send the PDF to the browser for download. Our article on "Generate HTML PDFs in CodeIgniter 4 with Dompdf" guides you step by step.

Chapter 5: API Creation and Advanced Topics

CodeIgniter 4 is not only ideal for monolithic applications, but it also offers tools to build robust RESTful APIs and handle interoperability with other platforms.

5.1. How to Create a REST (RestFul) API in CodeIgniter 4

REST (Representational State Transfer) APIs are fundamental for allowing your application to communicate with other services, mobile applications, or decoupled frontends. CodeIgniter 4 greatly facilitates the creation of RESTful APIs without the need for third-party libraries. Using ResourceController, you can define controllers that automatically map HTTP methods (GET, POST, PUT, DELETE) to the corresponding CRUD operations. You only need to specify the model ($modelName) and the response format ($format = 'json').

You can customize responses to include data, messages, and status codes, ensuring a predictable and easy-to-consume API. Data validation in the creation and updating of resources is crucial and integrates with the form validation system. For a complete guide on how to build your first RESTful API with CodeIgniter 4, consult "How to create a REST API (RestFul) in CodeIgniter 4".

5.2. Handling CORS the Easy Way

When your REST API is consumed by a frontend running on a different domain (e.g., a Vue application on localhost:5173 consuming your API on your-domain.com), you will face CORS (Cross-Origin Resource Sharing) issues. CORS is a security mechanism that restricts HTTP requests from different domains. CodeIgniter 4.5.0 onwards includes native support for CORS, allowing you to easily configure it in app/Config/Cors.php.

You can define allowed origins (allowedOrigins), HTTP methods (allowedMethods), and headers (allowedHeaders). It is crucial to handle "preflight requests" (OPTIONS requests) that the browser sends before POST, PUT, PATCH, etc. A correct configuration involves grouping your API routes and applying a cors filter that manages these headers. Avoiding manual solutions in public/index.php is key for a secure and maintainable implementation. All details can be found in "CORS in CodeIgniter 4, the easy way".

5.3. Creating Your Own Helpers

Helpers in CodeIgniter are collections of global PHP functions that you can call from anywhere in your application. They are ideal for encapsulating reusable logic and avoiding code repetition. CodeIgniter comes with a series of built-in helpers (for URLs, text, dates, etc.), but you can create your own in app/Helpers/. A helper is simply a PHP file that contains functions, which are loaded manually ($this->load->helper('helper_name')) or automatically through app/Config/Autoload.php.

For example, you could create a helper to format dates in a specific way. For more information on how to create and use your own helpers, consult "The helpers in CodeIgniter to define our functions".

5.4. Updating Old Versions to Modern Ones

Keeping your CodeIgniter project updated is essential for security and to take advantage of the latest features. When it comes to updating old versions (e.g., from CodeIgniter 3 to 4, or from a very old 4.x version to a more recent one), the safest and most recommended methodology is "copy and paste." It consists of:

Create a completely clean CodeIgniter 4 project with the latest version, using Composer.
Copy your application code (mainly the content of the app/ folder) from the old project to the new clean project.

This methodology, although it may seem rudimentary, saves you the tedious process of following manual update guides, which often involve renaming files, changing syntax, or adjusting internal configurations that have evolved. By copying your code to a newly installed framework, you ensure that all framework dependencies and configurations are up to date. More details in "Updating old versions of CodeIgniter 4 to a modern version".

Conclusion: CodeIgniter 4, a Current and Efficient Option

CodeIgniter 4 is presented as a robust, fast PHP framework with a learning curve that makes it ideal for both beginners and experienced developers. Its focus on simplicity, performance, and MVC organization allows you to build web applications efficiently, from a "Hello World" to complex RESTful APIs and data management systems.

We hope this definitive guide serves as an invaluable resource on your journey to master CodeIgniter 4. We encourage you to explore each of the linked articles to delve deeper into topics of interest and continue building quality web applications with this excellent framework. Happy developing!

Course and Book

Finally, if you want to learn CodeIgniter from 0 to 100, I recommend my course and book which are aimed at anyone who wants to start developing with CodeIgniter. It is a great framework to start developing if you don't want to complicate yourself with Laravel, which has a steeper learning curve, or you simply want to start a simple development and move from PHP to a great and very light framework.