Introduction

Upgrading from CodeIgniter 3 to CodeIgniter 4 is not a routine framework update—it is a full application migration that impacts project structure, namespaces, configuration, security, and long-term maintainability. Many businesses continue running CodeIgniter 3 applications even after end-of-life support, often due to concerns about compatibility issues, data safety, and production downtime. Based on real-world migration experience, a successful upgrade requires careful planning, controlled refactoring, and thorough testing rather than a simple version switch. In this guide, we explain what it actually takes to upgrade CodeIgniter 3 to CodeIgniter 4 safely, what challenges to expect, and when it’s better to involve experienced PHP developers for a reliable migration.

Our team has migrated legacy CodeIgniter 3 applications to CodeIgniter 4 for production environments where stability, data safety, and backward compatibility were critical requirements.

Why Upgrade from CodeIgniter 3 to CodeIgniter 4?

Before diving into the technical process, it’s important to understand why upgrading is worth the effort.

1. End of Long-Term Relevance

While CodeIgniter 3 still works, it lacks modern development standards such as:

Namespace support
PSR compliance
Advanced security handling
Native Composer integration

CodeIgniter 4 is actively maintained and built for modern PHP versions (PHP 7.4+ and PHP 8).

2. Improved Security

CodeIgniter 4 offers:

Stronger CSRF protection
Improved XSS filtering
Secure session handling
Better encryption services

This makes it significantly safer for production applications.

3. Modern Architecture

CodeIgniter 4 uses:

Namespaces
Dependency injection
Modular structure
PSR-4 autoloading

This results in cleaner, scalable, and maintainable codebases.

4. Performance & Scalability

With better request handling, optimized routing, and cleaner execution flow, CodeIgniter 4 performs better in large-scale applications.

Need Expert Help Upgrading from CodeIgniter 3 to CodeIgniter 4?

Upgrading from CodeIgniter 3 to CodeIgniter 4 is not a simple version update—it’s a framework migration that involves architectural changes, namespace handling, compatibility fixes, and extensive testing. For production applications, a poorly planned upgrade can lead to broken features, security issues, or unexpected downtime.

At Cyberorama, we help businesses safely migrate CodeIgniter 3 applications to CodeIgniter 4 with a structured, tested approach. Our experienced PHP developers handle the complete upgrade process, including code refactoring, dependency compatibility, data integrity checks, and performance optimization.

What We Handle for You

Full CodeIgniter 3 → CodeIgniter 4 migration
Compatibility analysis and refactoring
Secure handling of existing data and configurations
Thorough testing to avoid regressions and downtime
Performance and security optimization after migration

If you want to upgrade without risking your live application, you can hire experienced PHP developers who specialize in modern PHP frameworks and legacy system upgrades.

Hire PHP Developers
Explore Our Web Development Services

Key Differences Between CodeIgniter 3 and CodeIgniter 4

Upgrading is not a simple version bump. CodeIgniter 4 is architecturally different.

Major Differences at a Glance

Feature	CodeIgniter 3	CodeIgniter 4
PHP Version	5.6+	7.4+
Namespaces	❌ No	✅ Yes
MVC Structure	Basic	Advanced
Composer Support	❌ No	✅ Yes
Security	Limited	Enhanced
Configuration	Global files	Environment-based

Because of these changes, direct migration is not possible — the project must be upgraded thoughtfully.

Pre-Upgrade Checklist (Critical Step)

Before starting the upgrade, CyberOrama strongly recommends completing the following:

1. Audit Your Existing CodeIgniter 3 Project

Identify custom libraries
Review helpers and hooks
List third-party integrations
Check deprecated PHP functions
Review database usage

2. Backup Everything

Always create:

Full codebase backup
Database backup
Server configuration backup

3. Check PHP Compatibility

Ensure your server supports PHP 7.4 or higher, preferably PHP 8.x.

Step-by-Step Guide to Upgrading from CodeIgniter 3 to CodeIgniter 4

Step 1: Set Up a Fresh CodeIgniter 4 Installation

Start with a clean CodeIgniter 4 installation using Composer:

This ensures you’re working with the latest stable structure.

Step 2: Understand the New Folder Structure

CodeIgniter 4 introduces a modern directory layout:

app/ – Application logic
public/ – Public-facing files
writable/ – Logs, cache, sessions
env – Environment configuration

Unlike CI3, index.php is inside the public folder, improving security.

Step 3: Migrate Configuration Files

Configuration in CI4 is class-based instead of array-based.

Key files to migrate:

database.php
config.php
autoload.php
routes.php

You will need to rewrite configurations using CI4 syntax.

Step 4: Convert Controllers

Controllers now:

Use namespaces
Extend BaseController
Follow PSR-4 autoloading

CI3 Example:

class Welcome extends CI_Controller {
    public function index() {
        $this->load->view('welcome_message');
    }
}

Step 4: Convert Controllers

Controllers now:

Use namespaces
Extend BaseController
Follow PSR-4 autoloading

CI3 Example:

class Welcome extends CI_Controller {
    public function index() {
        $this->load->view('welcome_message');
    }
}

CI4 Equivalent:

class Welcome extends BaseController {
    public function index() {
        return view('welcome_message');
    }
}

Step 5: Update Models

Views require minimal changes, but:

$this->load->view() becomes view()
Variables are passed differently
Layouts can be handled using View Cells

Step 7: Rewrite Helpers & Libraries

CI4 helpers are loaded using:

Custom libraries must:

Use namespaces
Follow PSR-4 standards
Be placed in app/Libraries

Step 8: Database Query Changes

CI4 introduces:

Query Builder improvements
Better result handling
Improved transactions

Most CI3 queries will work, but manual verification is essential.

Step 9: Routes Migration

Routes are now defined explicitly:

Unlike CI3, automatic routing is discouraged for security reasons.

Step 10: Environment Configuration

CI4 uses .env files for:

Environment-specific settings
Database credentials
Debug mode

This allows safer production deployments.

Common Challenges During Upgrade

1. Third-Party Libraries

Many CI3 libraries are incompatible with CI4 and must be replaced or rewritten.

2. Legacy PHP Code

Older PHP syntax must be updated for PHP 7.4+ compatibility.

3. Session & Authentication Logic

CI4 handles sessions differently, requiring authentication rewrites.

Why Choose CyberOrama for CodeIgniter Upgrade?

At CyberOrama, we specialize in:

Legacy framework modernization
CodeIgniter 3 to CodeIgniter 4 upgrades
Performance optimization
Security hardening
Scalable architecture design

We don’t just migrate code — we future-proof your application.

Conclusion

Upgrading from CodeIgniter 3 to CodeIgniter 4 is a strategic investment in your application’s future. While the process requires planning, technical expertise, and careful execution, the benefits — security, performance, scalability, and maintainability — are well worth it.

If you’re running a legacy CodeIgniter 3 application and planning for growth, now is the right time to upgrade.

Contact CyberOrama today to modernize your CodeIgniter project with confidence.

Written by Cyberorama PHP Team

Frequently Asked Questions (FAQs)

1. What services does Cyberorama Web Development offer?

Cyberorama Web Development provides end-to-end digital services including custom website development, web application development, mobile app development (iOS and Android), eCommerce development, CMS solutions, payment gateway integration, website speed optimization, server technical support, and dedicated developer hiring services.

2. Do you offer custom website development services?

Yes, we specialize in custom website development tailored to your business goals. Our team builds secure, scalable, and SEO-optimized websites using modern technologies and frameworks to ensure high performance and long-term growth.

3. Can I hire dedicated developers from Cyberorama?

Absolutely. You can hire dedicated web developers including WordPress developers, Laravel developers, CodeIgniter developers, PHP developers, Shopify developers, and Next.js developers. We offer flexible hiring models such as hourly, monthly, and project-based engagement.

4. Do you provide WordPress development services?

Yes, we offer WordPress development services including custom theme development, plugin customization, WooCommerce store development, website maintenance, and managed hosting solutions.

5. Do you offer Laravel and CodeIgniter web application development?

We provide both Laravel and CodeIgniter web application development services. Our developers build high-performance, scalable, and secure PHP web applications, including SaaS platforms, dashboards, portals, and custom business solutions.

6. Can you build eCommerce websites?

Yes, we deliver eCommerce website development services using Shopify, WooCommerce, Magento, and custom PHP frameworks. Our eCommerce solutions are optimized for performance, security, and conversions.

7. Do you develop mobile applications?

Yes, we offer mobile app development services for both iOS and Android platforms. Our apps are designed for performance, scalability, and excellent user experience, following App Store and Play Store guidelines.

8. Do you provide payment gateway integration services?

We offer secure payment gateway integration services, including PayPal, Stripe, and Authorize.Net. Our integrations ensure fast, reliable, and PCI-compliant online transactions for eCommerce and web applications.

9. Can you help improve website speed and performance?

Yes, our website speed optimization services focus on reducing load times, improving Core Web Vitals, enhancing SEO performance, and delivering better user experience and higher conversion rates.

10. Do you provide CMS (Content Management System) solutions?

We deliver custom CMS solutions that allow businesses to manage content easily and securely. Our CMS services are scalable, user-friendly, and tailored to your workflow requirements.

11. Do you offer server technical support?

Yes, we provide server technical support services including server setup, monitoring, optimization, maintenance, security updates, and troubleshooting to ensure reliable and uninterrupted operations.

12. Can you work with existing or legacy projects?

Yes, we handle project upgrades, migrations, maintenance, and enhancements for existing websites and applications, including legacy PHP, WordPress, Laravel, and CodeIgniter systems.

13. Are your services SEO-friendly?

Yes, all our websites and web applications are built using SEO best practices, including clean code, fast loading speed, mobile responsiveness, and optimized structure for search engines.

14. What industries do you serve?

We work with startups, small businesses, enterprises, and agencies across industries such as eCommerce, SaaS, real estate, healthcare, education, finance, and professional services.

15. How can I request a quote for your services?

You can contact us through our website to request a free quote. Share your project requirements, and our team will get back to you with a tailored solution and pricing details.

16. Is CodeIgniter 4 backward compatible with CodeIgniter 3?

No, CodeIgniter 4 is not backward compatible with CodeIgniter 3. The framework introduces a new application structure, namespaces, updated configuration handling, and modern PHP standards. Because of these architectural changes, upgrading requires refactoring existing code rather than performing a simple version update. Proper planning and testing are essential to ensure a smooth migration.

17. How long does it take to upgrade from CodeIgniter 3 to CodeIgniter 4?

The timeline for upgrading from CodeIgniter 3 to CodeIgniter 4 depends on the size and complexity of the application. Smaller projects may take a few days, while larger or heavily customized applications can require several weeks. Factors such as custom libraries, third-party integrations, authentication systems, and data handling logic all affect the migration timeline.

18. Should I upgrade a live CodeIgniter 3 application or build a new CodeIgniter 4 version?

For most production applications, it is not recommended to upgrade directly on a live environment. A safer approach is to create a separate CodeIgniter 4 setup, migrate and refactor the code in stages, and thoroughly test functionality before deployment. This minimizes the risk of downtime, data loss, and unexpected issues during the upgrade process.