4.0 Upgrade Guide

First, check that your application is running on latest CakePHP 3.x version.


The upgrade tool only works on applications running on latest CakePHP 3.x. You cannot run the upgrade tool after updating to CakePHP 4.0.

Fix Deprecation Warnings

Once your application is running on latest CakePHP 3.x, enable deprecation warnings in config/app.php:

'Error' => [
    'errorLevel' => E_ALL,

Now that you can see all the warnings, make sure these are fixed before proceeding with the upgrade.

Upgrade to PHP 7.2

If you are not running on PHP 7.2 or higher, you will need to upgrade PHP before updating CakePHP.


CakePHP 4.0 requires a minimum of PHP 7.2.

Use the Upgrade Tool

Because CakePHP 4 adopts strict mode and uses more typehinting, there are many backwards incompatible changes concerning method signatures and file renames. To help expedite fixing these tedious changes there is an upgrade CLI tool:


The file_rename command and rector rules for cakephp40, and phpunit80 are intended to be run before you update your application’s dependencies to 4.0. The cakephp40 rector rules will not run correctly if your application already has its dependencies updated to 4.x or PHPUnit8.

# Install the upgrade tool
git clone https://github.com/cakephp/upgrade
cd upgrade
git checkout 4.x
composer install --no-dev

With the upgrade tool installed you can now run it on your application or plugin:

# Rename locale files
bin/cake upgrade file_rename locales <path/to/app>

# Rename template files
bin/cake upgrade file_rename templates <path/to/app>

Once you’ve renamed your template and locale files, make sure you update App.paths.locales and App.paths.templates paths in /config/app.php. If needed, refer to the skeleton app config.

Applying Rector Refactorings

Next use the rector command to automatically fix many deprecated CakePHP and PHPUnit method calls. It is important to apply rector before you upgrade your dependencies:

bin/cake upgrade rector --rules phpunit80 <path/to/app/tests>
bin/cake upgrade rector --rules cakephp40 <path/to/app/src>

You can also use the upgrade tool to apply new rector rules for each minor version of CakePHP:

# Run the rector rules for the 4.0 -> 4.1 upgrade.
bin/cake upgrade rector --rules cakephp41 <path/to/app/src>

Update CakePHP Dependency

After applying rector refactorings, upgrade CakePHP and PHPUnit with the following composer commands:

php composer.phar require --dev --update-with-dependencies "phpunit/phpunit:^8.0"
php composer.phar require --update-with-dependencies "cakephp/cakephp:4.0.*"


Next, ensure your src/Application.php has been updated to have the same method signatures as the one found in cakephp/app. You can find the current Application.php on GitHub.

If you are providing some kind of REST API, don’t forget to include the Body Parser Middleware. Finally, you should consider upgrading to the new AuthenticationMiddleware and AuthorizationMiddleware, if you are still using AuthComponent.