Code

Managed image allow to select image file, preview and remove.

Step 1. Create acustom module and a @FormElement usin the ManagedImage.php file

Step 2. Example of managed image

Import configuration file programmatically on Drupal 9 using config_update contrib module and service

//Update Module settings
\Drupal::service('config_update.config_update')->revert('system.simple', 'mymodule.settings');

State servic eallow to store variables such as state of the server temporarily or permanently

Examples:

Drupal settings file can contains variable which can use to use for different configuration in different environments.

Example:
env_name
default_info_nid

$settings['env_name'] = 'Local';
$settings['default_info_nid'] = 1';

You can use IMCE to select a file.

Method 1 : Form hook_page_attachments

This method allow to store data on drupal session using drupal session table (not php $_SESSION).
Storage is different for each users ans each visitors if anonymous

Syntax:

\Drupal::service('page_cache_kill_switch')->trigger();

Example on a controller:

Create a Drupal 9 project with composer

Error N°1 : PHPunit not found

If uou have a message like : Add Phpunit via composer

CAUTION : PHPunit Version >= 8 is not compatable with drupal, so use the 7

composer require --dev phpunit/phpunit:7