Upgrading older versions of CodeIgniter 4 to a modern version
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I've spent a considerable amount of time working with Laravel (which I consider superior), and I haven't updated my CodeIgniter 4 code in years.
Obsolete Project: My previous course, which you can find in the GitHub repository (by searching for "libre de desarrollo" and the CodeIgniter course), uses an already obsolete version of the framework. For example, the version used in 2022 probably referenced PHP 7.x, whereas the current version (recorded in 2025) requires PHP 8.x. Working with old versions exposes the project to potential vulnerabilities.
Recommended Update Methodology: Copy and Paste!
When working with frameworks that are created using commands (like Laravel, CodeIgniter, or Flutter), the best strategy for updating very old projects is:
Create a New Project: Generate a completely clean CodeIgniter 4 project using modern commands. This project will have the latest syntax, configurations, and updated libraries (e.g., the composer.json file will already be correct).
Copy the Implemented Code: Most of these frameworks divide the project into two blocks:
- The code generated by the framework.
- Your code (95% of the work).
In CodeIgniter, your code is primarily located in the app folder. You only have to copy the content you created (controllers, models, views, migrations, seeders, etc.) and paste it into the clean project.
Advantage: This methodology saves us the tedious process of following manual upgrade guides, which often require renaming files, changing syntax, or adjusting internal framework configurations that have evolved since their release.
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I'm talking about how you can easily update an old project in C4 to a modern version. One of the problems we have is that the C4 team tends to change files like index.php, configurations, dependencies, which can be a mess if you have a very old project.