Difference Between CodeIgniter 3 And 4: Everything You Need To Know

You have probably heard about the CodeIgniter framework for web development and wondered why it’s so popular. What makes it powerful? And what is the difference between CodeIgniter 3 and 4? If you are looking for answers to these questions and more, this blog goes in-depth to provide you with all the relevant information you need.

What is CodeIgniter?

CodeIgniter is one of the most powerful open-source PHP web development frameworks widely used for building dynamic web applications and websites. The framework uses MVC modeling to provide better efficiency, simplicity, and an optimized development process.

The CodeIgniter framework is packed with built-in libraries to provide core functionalities, including database and session management. It has a logical structure and an intuitive user interface to give developers the best tools to create highly efficient web applications.

The evolution of the CodeIgniter framework

The CodeIgniter framework has seen several updates and improvements throughout the years, with CodeIgniter 4 being the latest version. CodeIgniter was first released in February 2006 and has since undergone significant changes.

The first change came in October 2011 with the release of CodeIgniter 2.0, which included significant enhancements such as support for the model–view–controller (MVC) architectural pattern, improved error handling, and increased performance.

The second significant change came in October 2014 with the release of CodeIgniter 3.0, which included new features like full-page caching, improved security, and an updated codebase that is easier to maintain and extend.

CodeIgniter 4 was released in February 2020, bringing a slew of features and security upgrades to provide an enhanced experience to developers. Since its initial release, millions have downloaded CodeIgniter extensively, making it one of the most popular web application frameworks today.

Key differences between CodeIgniter 3 and CodeIgniter 4

There are some prominent differences in the CodeIgniter 4 version compared to its third generation. Here are some crucial points of difference between CodeIgniter 3 and 4 to help you grasp the upgrades and new features in the latest version.


A major difference between CodeIgniter 3 and 4 is the new file structure or directory. CodeIgniter 3 only had two directories in the form of /system and /application for storing the files. The directory structure has been upgraded in CodeIgniter 4 by providing five directories in the form of /app, /public, /system, /writable, and /tests. This provides a better distribution of files based on their domains or types.

PHP version

There was a gap of almost five years between CodeIgniter 3 and CodeIgniter 4, which saw the release of several newer versions of PHP. To use the latest CodeIgniter 4 version, you need a minimum PHP version of 7.2, whereas you could use CodeIgniter 3 with PHP version 5.6, which is now discontinued. Thus the latest CodeIgniter version is compatible with the latest PHP versions to take advantage of its new features and updates.


CodeIgniter 4 provides more efficient and superior performance than the CodeIgniter 3 version. Since CodeIgniter 4 requires developers to use a minimum PHP version of 7.2, it takes advantage of the latest features in PHP to deliver an optimum experience to the developers.

In addition, CodeIgniter 4 uses lazy loading, which results in significant performance gains. In CodeIgniter 3, helpers and libraries must be loaded manually, while in CodeIgniter 4, they can be autoloaded. This change provides better optimization and reduces the amount of code needed to start a project.


There is no namespace usage in CodeIgniter 3, whereas the CodeIgniter 4 framework is based on PHP 7.2 or later versions. Hence, everything within the framework uses namespaces except for helpers. Namespaces enable the placement of controllers in distinct folder structures and then link the routes to the application. This provides a more streamlined structure to the framework, improving performance and efficiency.


CodeIgniter 4 provides a more optimized autoloading process partly because of the implementation of namespaces. In CodeIgniter 3, you had to manually configure most of the files for loading; the autoloading feature in CodeIgniter 4 has made the whole process faster and more dynamic.

Backward compatibility

When it comes to migration from one version to another, the CodeIgniter 4 is not backward compatible. This means that when you are migrating from CodeIgniter 3 to CodeIgniter 4, you will need to do a lot more work in terms of settings and configuration than migrating from CodeIgniter 2 to CodeIgniter 3, where you just needed to overwrite the files in the system. When migrating to CodeIgniter 4, you need a new structure; therefore, a rewrite of all the classes is required.

The importance of migrating to the latest version of CodeIgniter

As with almost all applications and software systems, it is critical to update your programs regularly. This is especially important because the new updates provide better features, optimized functionality, and improved performance and usually offer enhanced security to ensure your software applications are safe and secure.

When you run older versions of applications or frameworks, they tend to be incompatible with the latest collaborative tech stack, leading to the general decline in performance which impacts productivity and overall experience. These updates also help improve the stability and iron out any bugs or errors in the previous version. This is why, if you are still running CodeIgniter 3, it makes sense to upgrade it to the latest version.

Hiring CodeIgniter developers

If you are building a web development project, CodeIgniter is one of the best PHP frameworks for developing dynamic web applications. To execute your project, you will need access to reliable and highly qualified CodeIgniter developers in the industry. It is critical to have a robust and reliable hiring funnel to hire a CodeIgniter developer with high levels of expertise and extensive experience in the web development framework.

Before starting the hiring process, you should draft lucid job descriptions mentioning all the essential skills needed, job roles & responsibilities, benefits, and salary range. Once done, you must prepare a healthy question bank containing all the relevant technical questions related to the CodeIgniter PHP web development framework that you need to filter qualified candidates. You must also evaluate the developers for their soft skills to ensure they fit in well with your organization’s culture.

Apart from hiring through conventional job boards, you also have the option to go with AI-powered recruitment platforms that provide automated sourcing, matching, vetting, and management of developers to help you scale your development team quickly.

Wrapping up

Now we have seen the difference between CodeIgniter 3 and 4; it makes a lot of sense to upgrade to the latest version to enjoy the numerous benefits and features that come with it. It is vital to keep updating to the latest versions to harness the power of modern functionalities and integration with updated PHP. When you hire CodeIgniter developers, you must ensure that they are aware of the latest updates and are proficient in working with the framework as a whole.

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