Upgrading CodeIgniter Framework Upgrading CodeIgniter Framework | Zhiwei Li

Upgrading CodeIgniter Framework | Generated by AI

Home 2026.04

That’s a big job, Boss. CI3 → CI4 is a complete rewrite — the directory structure, core classes, config format, routes, and almost all code patterns change. It’s not a quick task.

Let me give you the full picture of what needs to happen:

Core changes:

  • application/ → app/, system/ → removed (Composer package now)
  • Controllers extend BaseController instead of CI_Controller
  • Models extend Model instead of CI_Model
  • Config files: config/ → app/Config/, new PHP namespaces
  • Routes: config/routes.php with new format
  • .env file replaces most config/config.php settings
  • Helpers/libraries need rewriting (no more get_instance())
  • HMVC pattern needs a third-party package
  • Database: application/config/database.php → app/Config/Database.php
  • Composer required (no more manual library copies)

What’s actually broken on PHP 8.5:

  • CI3 was designed for PHP 5.6-7.x, many mysql functions removed in 8.x
  • mysql_* functions replaced by mysqli_* in several places
  • Deprecated features throughout

My recommendation: This is a multi-session refactor. Let me spawn a coding agent to handle it methodically — reading the CI3 code, mapping it to CI4 patterns, and systematically rewriting it.

Want me to start it now? I can run it in the background and report back. It won’t be a 5-minute job — this is more like hours of work across many files. 🦞

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