CodeIgniter Development: Maintain, Secure, Upgrade or Migrate
An honest guide to CodeIgniter today: how we maintain and secure CodeIgniter 3 apps, what moving to CodeIgniter 4 really involves, and when Laravel makes more sense.
If you are looking into CodeIgniter development today, you most likely have an application that works. It was built quickly, it runs part of the business, and it has grown for years. Now the PHP version needs an upgrade, a security review has raised issues, or the developer who knew it best has moved on.
Good looks like a clear decision and a safe path: an application that is patched and hardened now, running on a supported PHP version, with a realistic plan for what comes next. That might mean staying on CodeIgniter 3 for a while, converting to CodeIgniter 4, or moving to Laravel. We help with all three, and we will tell you which one we would choose.
Where CodeIgniter development still makes sense
CodeIgniter earned its following by being small. It runs on ordinary hosting, needs little configuration, and a developer can follow the whole request lifecycle in an afternoon. Many corporate websites, business portals and internal tools were built on it for exactly those reasons, and plenty still do their job well.
CodeIgniter 4 keeps that lightness and adds what modern PHP expects: namespaces, Composer, a separate public web root, environment files, filters for cross-cutting concerns, explicit routes by default, a command-line tool for migrations and scaffolding, and a real testing toolkit. It is actively maintained by the CodeIgniter Foundation. For small to mid-sized applications looked after by a team that knows the framework, it remains a reasonable home.
CodeIgniter 3 is a different story. It is the legacy line, and the project’s effort now goes into version 4. Running it is still possible, but it needs care.
Maintaining and securing a CodeIgniter 3 application
When we take over a CodeIgniter 3 app, we start with an audit and a hardening pass. The same issues come up again and again:
- Framework folders inside the web root. By default the application and system folders sit beside index.php, protected only by .htaccess files, which Nginx ignores. We move both above the web root.
- CSRF protection switched off. It ships disabled. We enable it and fix the forms and AJAX calls that relied on its absence.
- Every public controller method is a URL. Helper methods left public become reachable endpoints. We make them private or protected and review the routes.
- SQL built from strings. The Query Builder and query bindings escape values; concatenated queries do not. We replace them.
- Input filtering instead of output escaping. Global XSS filtering was never a substitute for escaping in views, by context. We escape on output.
- Weak session and cookie settings. Sessions get a private save path or a database or Redis driver, cookies get Secure and HttpOnly flags, and the session ID is regenerated at login.
- Outdated cryptography. The old mcrypt-based Encrypt library goes, and password hashes move to
password_hash(), upgraded at each user’s next login. - Errors on screen. The environment is set to production, so errors are logged and never displayed.
Before changing any of this, we put a safety net in place. CodeIgniter 3 was not designed around automated testing, so we write HTTP-level tests against a staging copy that cover login, the main forms and anything that touches money. Third-party libraries that were copied into the application folder by hand are replaced with Composer packages, which CodeIgniter 3 can load, so they can be versioned and audited.
Then comes PHP itself. CodeIgniter 3 can usually run on current PHP versions, but each jump brings deprecation warnings, and the framework core sometimes needs small patches. We upgrade PHP in steps, running those tests at every step and watching the logs closely after each release. When aging shared hosting blocks the upgrade, we move the application to hosting you control.
Upgrading from CodeIgniter 3 to CodeIgniter 4
This is the step most teams underestimate. CodeIgniter 4 is a rewrite, not a new release of the same code, and its own upgrade guide describes the move as converting an application rather than upgrading it. In practice:
- Controllers, models and libraries become namespaced classes loaded through Composer’s autoloader.
- The loader pattern, where you load a model and then reach it as a controller property, gives way to services, factories and helpers.
- Input, sessions, validation and database results all have new APIs, so almost every controller changes.
- Hooks become events and filters, and configuration arrays become configuration classes.
- Some CodeIgniter 3 libraries have no direct equivalent and need replacing.
The database stays as it is, and views and business rules usually carry over with modest changes. The plumbing around them does not.
How we run the conversion
Small applications we convert in one pass, behind a short feature freeze and a full regression run. Larger ones we convert in sections. Both versions run side by side on the same domain and database, and the web server routes converted sections to CodeIgniter 4 while the rest stays on CodeIgniter 3.
Login and sessions get a deliberate bridge first, so users never notice which side is serving them. The HTTP-level tests written during hardening become the acceptance tests for the conversion: a section switches over only when its existing tests pass against the new code and QA signs off.
When to move to Laravel instead
Because the conversion to CodeIgniter 4 touches almost every file, it is fair to compare it with a move to Laravel. The effort is often closer than teams expect, and the destination is very different.
| Your situation | What we usually recommend |
|---|---|
| Stable app, few changes planned, tight budget | Stay on CodeIgniter 3 for now: harden it, upgrade PHP, plan the exit |
| Small to mid-sized app, mostly forms and reports, team knows CodeIgniter | Convert to CodeIgniter 4 |
| Growing product that needs queues, scheduled jobs, real-time features, rich APIs or a capable admin panel | Move to Laravel |
| You plan to hire and grow a PHP team | Move to Laravel, for its larger ecosystem and hiring pool |
| The application will be retired soon | Harden and contain it; skip the conversion |
Laravel brings first-party queues with a monitoring dashboard, a scheduler, authentication scaffolding, real-time broadcasting and several mature admin panel options. If your roadmap needs those, building them yourself on CodeIgniter will cost more over time than the move. If it does not, CodeIgniter 4 is lighter and closer to what your developers already know.
How a CodeIgniter engagement works
Most CodeIgniter work starts as a focused engagement. We sign an NDA, get read access to the repository and details of the hosting setup, and deliver a written audit: security findings ranked by severity, the PHP and dependency upgrade path, current test coverage, and a stay, convert or move recommendation with the reasoning behind it.
The delivery team is small: an engineer who knows both CodeIgniter lines, a QA tester who builds the regression suite before anything changes, and a business analyst when undocumented behavior has to be pinned down with the people who use the system. You get regular written reports, a staging environment to test on, and every change in your own repository. The wider engineering practices behind this, from static analysis to deployment, are described in our PHP development guide.
Frequently asked questions
Is CodeIgniter 3 still safe to run?
It can be, with work: a hardening pass, a supported PHP version, careful patching and monitoring. It should not be the foundation for a long new roadmap.
Can we move from CodeIgniter 3 to 4 gradually?
Yes. Running both versions side by side on the same database and moving one section at a time is how we handle larger applications. Shared login and sessions are set up first.
What survives the conversion?
Your database, most of your views and your business rules. Controllers, models and libraries need the most work, because the framework APIs around them changed.
Is Laravel always better than CodeIgniter 4?
No. Laravel is broader, not automatically better. For a compact application maintained by a team that knows CodeIgniter, version 4 is often the more economical choice.
Do you start new projects on CodeIgniter?
Rarely. For new PHP products we usually recommend Laravel, and we choose CodeIgniter 4 when a client’s team, hosting or existing code makes it the sensible option. If you are planning a new build, our web application development article explains how we approach one.
If a CodeIgniter application is carrying part of your business, the first step is knowing exactly where it stands. Tell us about your application, and we will propose an audit and an honest path forward.
