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CodeIgniter
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Upgrading Legacy CodeIgniter 3 Projects to Modern CodeIgniter 4

A practical step-by-step roadmap for refactoring CodeIgniter 3 codebases into modern PSR-4 namespaced CodeIgniter 4 applications.

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3 weeks ago

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Modernizing Legacy PHP Codebases

Upgrading from CodeIgniter 3 to CodeIgniter 4 brings support for PHP 8.2+, modern OOP namespaces, dependency injection, and integrated CLI migration tools.

Migration Checklist

  1. Namespacing: Convert procedural models and libraries to PSR-4 class structures in App\Models and App\Libraries.
  2. Database Queries: Replace legacy Active Record methods with CI4 QueryBuilder or Entity classes.
  3. Routing: Define explicit route definitions in app/Config/Routes.php.

Upgrading ensures legacy applications gain long-term security maintenance, microsecond execution speeds, and modern developer tooling.