Finally, we are one more step closer to Drupal 9. In order to make your Drupal 8 website ready for Drupal 9, you will need to update your existing website to Drupal 8.8, the latest stable release in 8.8.x branch. This branch removes all the incompatible APIs and prepares your website for Drupal 9. And which is why, It is highly recommended that you update to 8.8.
Before you start with the update, make sure you take backup of your website (code base & DB) or preferably, carry out this process on a staging site or on your local Drupal 8 set up. For this, it is assumed that you have composer installed for your Drupal 8 environment.
The first step is to modify composer.json manually.
1. Unset / empty
Once you are done with modifying the composer.json, it is time to execute a few commands with composer on CLI.
Execute composer commands
composer remove webflo/drupal-core-strict --no-update
composer remove drupal/core --no-update
composer require 'composer/installers:^1.7' --no-update
rm -rf core
rm -rf vendor
composer require drupal/core-recommended:^8.8 --update-with-dependencies
Now, site back and relax while composer performs the update.
Once the updates are downloaded, it is time to perform the db updates using
Congratulations! You have successfully updated your existing Drupal 8 website to 8.8 and you are now ready for Drupal 9!