Versioning Your 100+ Controllers in CI3 Without Changing a Single Route

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Introduction

Ever faced this?

"How can I refactor 100+ controllers in a live CI3 app without touching routes or breaking frontend code?"

This was my reality on a legacy CodeIgniter 3 project. I had to add new features and restructure logic without breaking thousands of AJAX/API calls already in production.

Here’s how I did it using custom router logic and a versioned controller directory, all without touching the routes file.

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🧠 The Problem

I had to:

• ✨ Refactor 100+ controller methods

• ➕ Add new features

• 🔒 Preserve all existing frontend AJAX/API endpoints

But without:

• ❌ Editing 1000+ frontend calls

• ❌ Manually redirecting each old method

• ❌ Renaming existing controller files

I needed a smarter, safer way to version my logic — just like APIs, but at the controller level.

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❌ What I Didn’t Want to Do

• Update every route or endpoint manually

• Add redirect() logic inside hundreds of methods

• Rename controllers and risk breaking everything

Too risky. Too time-consuming. Too boring.

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✅ The Solution: Router-Level Controller Versioning

I created a localized/ folder inside the controllers/ directory and duplicated all controllers that needed changes into it. Then, I modified the router to check this versioned folder first.

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🗂️ Folder Structure

Before:

application/
└── controllers/
    ├── Dashboard.php
    ├── Automation.php
    └── ... (100+ controllers)

After:

application/
└── controllers/
    ├── Dashboard.php
    ├── Automation.php
    └── localized/
        ├── Dashboard.php
        ├── Automation.php
        └── ... (100+ controllers)

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🛠️ Custom Router (MY_Router.php)

Inside application/core/, I created MY_Router.php and added the following:

<?php defined('BASEPATH') OR exit('No direct script access allowed');

class MY_Router extends CI_Router {
    protected function _validate_request($segments) {
        if (empty($segments)) {
            return $segments;
        }

        // Get controller segments (ignore method name)
        $controller_segments = $segments;
        if (count($segments) >= 2) {
            array_pop($controller_segments);
        }

        // Build the file path for the versioned controller
        $localized_file = APPPATH . 'controllers/localized/' . implode('/', $controller_segments) . '.php';

        // If versioned controller exists, load it
        if (file_exists($localized_file)) {
            array_unshift($segments, 'localized');
            log_message('debug', 'Using localized controller: '.$localized_file);
        } else {
            log_message('debug', 'Localized controller not found: '.$localized_file);
        }

        return parent::_validate_request($segments);
    }
}

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🔍 How It Works

• 🔎 CI3 checks if the controller exists in the `localized/` folder

• ✅ If yes, it uses the updated controller

• 🔁 If no, it falls back to the original

• 🛡️ No route changes required — the frontend still uses the same URLs

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🧪 Real-World Impact

• ⚙️ Easy rollout of new features controller-by-controller

• 🔁 Seamless fallback to old code during testing

• 🚫 Zero downtime or broken frontend calls

• 🔍 Safer QA and debugging in production

• ⏱️ No need to touch thousands of routes or AJAX calls

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🧰 Tech Stack Used

• PHP (CodeIgniter 3)

• MySQL

• jQuery & AJAX frontend

• Webhook/Event-based triggers

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📚 Lessons Learned

• CI3 may be old, but it's still flexible when used smartly

• Versioning isn't just for APIs — it's great for controllers too

• A clean router design can help prevent future tech debt

• Avoiding unnecessary redirects reduces debugging headaches

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🏁 Final Thoughts

If you're working on a large CI3 codebase and need to modernize without disrupting the existing system, this router-based controller versioning approach could save you hours — or even days — of work.

It’s simple, non-intrusive, and gives you a safe playground for upgrades while keeping production stable.

Happy coding! 🚀

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✉️ Let me know in the comments if you’ve faced similar challenges — or if you’ve found other clever ways to handle large-scale controller refactoring in CI3!