Job codeigniter-3-app-to-codeigniter-4 · revised 9 October 2026
Convert one small CodeIgniter 3 app to CodeIgniter 4
Inventory every route in a small CodeIgniter 3 app, convert its production paths to CodeIgniter 4, and test five key flows in depth before the site holder switches it live.
You might be seeing
- The app says CodeIgniter 3 and the host is removing its old PHP version
- A new host or developer will only maintain CodeIgniter 4
- Routes or forms stop working after a naive framework-file replacement
No passwords, keys, card details or admin invites needed to start.
What usually happened
CodeIgniter 4 is a different application structure from CodeIgniter 3. Copying in new framework files does not carry over controllers, routes, filters, config, database access and view behaviour. An old business app needs its own workflows moved and checked on a copy, not a “version switch” in hosting.
Who it’s for: Owner of a custom CodeIgniter 3 application whose developer has left, who needs it maintained on a supported host and PHP version.
Usually starts when: The host is ending support for the old PHP runtime, or an agency says the app must move beyond CodeIgniter 3 before it can keep maintaining it.
The result: One CodeIgniter 3 application’s agreed login, read and write flows work in a CodeIgniter 4 staging version, with changed source and database migration steps ready for the authorised site holder.
Check whether this job fits
Four questions, about two minutes. Your answers stay on this page unless you choose to email them.
Checks you can run yourself
Check the version in the source
If you or your site holder have a backup, look for the VERSION value in system/core/CodeIgniter.php. Do not send the file or passwords in the first email.
Look for: A value beginning 3 means this job may fit; a value beginning 2 needs a different assessment.
What you get
- A map of the old routes and their CodeIgniter 4 equivalents
- The moved application source and dependency list with test results for the agreed flows
- Database and configuration change notes with staging deployment and rollback steps
Included
- One small CodeIgniter 3 application with one database, a bounded route inventory and up to five critical business flows
- Inventory and convert every production route, controller, model, filter, view and scheduled/API path needed for live use
- Move existing behaviour into a CodeIgniter 4 structure without redesigning the business flows
- Smoke-check every inventoried route and API response, and deeply test the five critical flows on a safe copy
Not included
- A CodeIgniter 3 app that only needs a PHP-version compatibility patch
- WordPress or Laravel applications
- New features, redesign or changing the database platform
- Rewriting undocumented third-party packages with no CodeIgniter 4 equivalent
- Live deployment or production credentials
How we know it’s done
Agreed with you before work starts. Each check produces evidence you keep.
Every inventoried production route has a CodeIgniter 4 equivalent with the expected status and access restriction on staging
Evidence: Complete route map and smoke-check result for normal and unauthorised test users
The five agreed critical flows each read and write the expected test records once, and every other inventoried route responds with its expected status
Evidence: Before/after test records and flow checklist
Staging logs show no framework fatal errors during the named flows, and the dependency install succeeds on the agreed PHP runtime
Evidence: Redacted error log and dependency install output
A restore on a test environment brings back the CodeIgniter 3 app and the pre-migration database snapshot
Evidence: Restore log and old-app test result
Sign-off. You review the full route/API inventory and the five deep-flow results before your holder switches live. Any untestable production path is a release blocker or a separately agreed exception.
If it fails. If the agreed acceptance checks do not pass, the client does not pay, and keeps our findings and rollback steps.
When it fits, and when we stop
It fits when
- The app is CodeIgniter 3, and the source and database schema are available
- Someone can create a safe copy of the files and a sanitised database
- You can name up to five flows the business needs to keep working
- A site holder can approve the staging result and deploy it under your account
- Every required live route and API consumer can be listed and smoke-tested, not only the five headline workflows
We stop and tell you if
- An essential closed-source package has no CodeIgniter 4 compatible version or replacement
- There is no safe way to copy and test the database without exposing regulated data
- The app is really CodeIgniter 2 or a customised framework fork with no clear upgrade route
- A database change is irreversible and there is no rehearsed restore
- The route/API inventory is too large or undocumented to fit the agreed small-app conversion scope
What could go wrong
Keep the CodeIgniter 3 app and its database snapshot untouched until the new one is signed off. If a live check fails, the holder points traffic back after reconciling any records created on the new app.
Scroll the table sideways to read it all.
| Risk | How we handle it |
|---|---|
| Moving routes changes access controls and exposes a private page | Map each old route and its filters, then test unauthorised access on staging. |
| Different database or session handling changes records silently | Compare read/write results against a test snapshot and review every session/data change. |
| Cutover loses records created in the old app after the first copy | Agree a brief write pause and final sync; retain both copies until the owner verifies the latest record. |
An independent reviewer checks the source route mapping, session/authentication and database-change tests, plus the cutover and way back.
How we deliver
We arrange the work and independent review, then show you the result against the agreed checks. You keep authority over your systems.
- Inventory every old production route, library, filter, API consumer and scheduled path, including the five flows chosen for deeper tests
- Convert every required live route and background path into the CodeIgniter 4 app; rehearse any database migration
- Smoke-check every inventoried route and API status, and deeply test the five critical flows with fake data and captured mail
- Have an independent reviewer check auth/session changes and database queries
- Hand over source, route map, results and rollback steps to the client’s site holder
This is a one-off job, not emergency cover or a subscription. We confirm eligibility, the total price, a start window and a delivery date before you accept. Work starts only after agreed inputs, secure access, any licences and necessary permissions are in place. Hosting, platform and supplier charges are excluded unless the written quote includes them. No charge or booking is created by an enquiry.
Need to keep it working?
After the conversion, discuss maintaining the supported runtime and rerunning the agreed business flows when dependencies change.
Ongoing work is separately scoped and quoted: no monitoring, response-time guarantee or automatic subscription is included in this job.
Explore an ongoing engineering lane, or mention the responsibility you need in your enquiry.
What you can check
This is a new service. We have not delivered this job for a client yet.
Other ways to get this done
- If only one page broke after a PHP version change, fix that specific runtime error first. Rebuilding the whole framework for one error may be unnecessary.
- CodeIgniter publishes an upgrade guide from 3 to 4, which a developer who holds your source can follow and test against your workflows.
Questions
Can the host just update CodeIgniter for us?
CodeIgniter 4 changes the application structure. Ask the host whether it means a full application move or just updating the PHP setting.
Does this include new features?
No. It carries over every agreed, inventoried production path, with five critical business flows tested in depth. New features need their own scope and price.
Start with an email
Send us
- The app’s address, CodeIgniter version and current PHP version if known
- The five pages or flows staff use most, including one that changes a record
- Any host deadline or notice about the old runtime
- Who owns the source, database and hosting accounts
Later, once you agree
- A copy of the source with configuration secrets removed
- A sanitised database copy and test logins with no real customer data
- A staging location and an authorised holder to deploy the approved change
- A company-controlled secure handoff agreed before access: no live passwords, keys, private code or customer records by ordinary email.
The client owns the accounts, domain, live system and keys. An AI agent prepares the change using only an authorised test copy or read-only information; a separate reviewer checks the risks, and the client or their site holder approves any live change. Synthetic Industry is owned by a person and remains accountable for the agreed work. We never ask for passwords in the first enquiry.
Or write to hello@syntheticindustry.ai with “codeigniter-3-app-to-codeigniter-4” as the subject.