Migrate CodeIgniter to Laravel Without Pain

Why does this look so familiar?

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$this->load->view('header');
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$data['users'] = $this->user_model->get_all();
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$this->load->view('user_list', $data);
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$this->load->view('footer');

What is wrong with this code? Nothing, if it is 2012. If it is 2024, it is a liability. I hear people say that you must do a big-bang rewrite to move away from CodeIgniter to a modern framework like Laravel. They claim it is the only way to escape technical debt. I disagree.

The big-bang myth

People believe in the big-bang rewrite because it sounds clean. Just shut down, build, and deploy. In reality, it is a nightmare. It creates huge regressions and stops all feature work for months. You should only rewrite if the core domain model is fundamentally broken or the language version is so old it poses a security risk.

Instead, use the strangler-fig pattern. Keep your old app running while you peel off features into Laravel. You can proxy traffic at the web server level, like Nginx or Apache, to direct specific routes to the new app.

Routing is your bridge

Here is the trick. Set up your Laravel app to sit behind the same proxy. If the request is for /users, let the legacy app handle it. If it is for /orders, pass it to Laravel. It works well until you hit shared state. (Yes, you will have to sync your sessions or database eventually.)

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location /orders {
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    proxy_pass http://laravel-app;
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}
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location / {
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    proxy_pass http://codeigniter-app;
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}

Does this solve everything?

“But won’t I have two versions of the truth?” you ask. That is fair. You will struggle with authentication across both apps for a bit. I usually solve this by having the legacy app issue a JWT that Laravel can verify, or by syncing the database tables directly. It isn’t pretty, but it keeps the lights on while you ship value.

I admit, if your app is deeply coupled with custom libraries that are impossible to extract, this approach gets messy fast. Sometimes, you just have to bite the bullet and rewrite the whole thing. I haven’t found a clean way to deal with extremely bespoke global helper functions (I’ve spent many hours cursing helper files in my career).

Take it slow

Start with the least risky, read-only parts of your application. Don’t try to move the user management system first. Move a reporting page or a static dashboard.

Keep the legacy codebase clean enough to maintain while you are in the transition phase. You are not just building; you are managing a migration. Do you really need to touch that old code? Maybe not. Can you build the next feature in Laravel instead of the legacy app? That is where you win.