Upgrading from 4.1.9 to 4.2.0

Please refer to the upgrade instructions corresponding to your installation method.

Mandatory File Changes

index.php and spark

The following files received significant changes and you must merge the updated versions with your application:

  • public/index.php

  • spark


If you don’t update the above two files, CodeIgniter will not work at all after running composer update.

The upgrade procedure, for example, is as follows:

composer update
cp vendor/codeigniter4/framework/public/index.php public/index.php
cp vendor/codeigniter4/framework/spark .


The constants EVENT_PRIORITY_LOW, EVENT_PRIORITY_NORMAL and EVENT_PRIORITY_HIGH are deprecated, and the definitions are moved to app/Config/Constants.php. If you use these constants, define them in app/Config/Constants.php. Or use new class constants CodeIgniter\Events\Events::PRIORITY_LOW, CodeIgniter\Events\Events::PRIORITY_NORMAL and CodeIgniter\Events\Events::PRIORITY_HIGH.


If you use Composer, when you installed CodeIgniter v4.1.9 or before, and if there are App\\ and Config\\ namespaces in your /composer.json’s autoload.psr-4 like the following, you need to remove these lines, and run composer dump-autoload.

    "autoload": {
        "psr-4": {
            "App\\": "app",             <-- Remove this line
            "Config\\": "app/Config"    <-- Remove this line

Breaking Changes

  • The system/bootstrap.php file no longer returns a CodeIgniter instance, and does not load the .env file (now handled in index.php and spark). If you have code that expects these behaviors it will no longer work and must be modified. This has been changed to make Preloading easier to implement.

Breaking Enhancements

  • The method signature of Validation::setRule() has been changed. The string typehint on the $rules parameter was removed. Extending classes should likewise remove the parameter so as not to break LSP.

  • The method signature of CodeIgniter\Database\BaseBuilder::join() and CodeIgniter\Database\*\Builder::join() have been changed. The string typehint on the $cond parameter was removed. Extending classes should likewise remove the parameter so as not to break LSP.

Project Files

Numerous files in the project space (root, app, public, writable) received updates. Due to these files being outside of the system scope they will not be changed without your intervention. There are some third-party CodeIgniter modules available to assist with merging changes to the project space: Explore on Packagist.


Except in very rare cases for bug fixes, no changes made to files for the project space will break your application. All changes noted here are optional until the next major version, and any mandatory changes will be covered in the sections above.

Content Changes

The following files received significant changes (including deprecations or visual adjustments) and it is recommended that you merge the updated versions with your application:

  • app/Config/Routes.php
    • To make the default configuration more secure, auto-routing has been changed to disabled by default.

All Changes

This is a list of all files in the project space that received changes; many will be simple comments or formatting that have no effect on the runtime:

  • app/Config/App.php

  • app/Config/Constants.php

  • app/Config/ContentSecurityPolicy.php

  • app/Config/Database.php

  • app/Config/Events.php

  • app/Config/Feature.php

  • app/Config/Filters.php

  • app/Config/Format.php

  • app/Config/Logger.php

  • app/Config/Mimes.php

  • app/Config/Publisher.php

  • app/Config/Routes.php

  • app/Config/Security.php

  • app/Config/Validation.php

  • app/Config/View.php

  • app/Controllers/BaseController.php

  • app/Views/errors/html/debug.css

  • app/Views/errors/html/debug.js

  • app/Views/errors/html/error_404.php

  • app/Views/errors/html/error_exception.php

  • app/Views/errors/html/production.php

  • app/Views/welcome_message.php

  • app/index.html

  • preload.php

  • public/index.php

  • spark