How to upgrade Yii to a newer version?

@dedrick 

To upgrade Yii to a newer version, follow these steps:

1. Check the documentation: Before upgrading, make sure to check the Yii upgrade guide to make sure there are no breaking changes that could affect your application.
2. Backup your code: Before upgrading, backup your existing codebase so that you can roll back if needed.
3. Update the composer.json file: Update the "yii2" package version in your composer.json file as per the latest version.
4. Run Composer update: Run the composer update command in your terminal to update the Yii2 package to the latest version.
5. Update configuration files: Check if your configuration files need any modifications as per new version guidelines.
6. Test: Once you have upgraded Yii, test all the functionalities of your application to ensure it is working as expected.
7. Deploy: Once you are confident that everything is working as expected, deploy your upgraded codebase.

Note: If you have several third-party extensions, make sure to check their compatibility with the upgraded Yii version and update them accordingly.