Creation in Drupal 9: A Step-by-Step Guide to Programmatically Add Users with Code Examples.

To programmatically create a user account in Drupal 9, you can use the user_save() function. However, starting from Drupal 8, the user_save() function is deprecated, and the recommended way is to use the User entity and the entity_save() method. Here's an example code snippet with a line-by-line explanation:

// Include necessary files and namespaces.
use Drupal\user\Entity\User;
use Drupal\Core\Password\PasswordInterface;

// Create a new user entity.
$user = User::create();

// Set the username for the new user.
$user->setUsername('new_username');

// Set the email address for the new user.
$user->setEmail('user@example.com');

// Set the password for the new user. You should hash the password using the password service.
$password = 'user_password';
$hashed_password = \Drupal::service('password')->hash($password);
$user->setPassword($hashed_password);

// Set the status of the user account (1 for active, 0 for blocked).
$user->activate();

// Set additional fields if needed.
// $user->set('field_name', 'field_value');

// Save the user entity.
$user->save();

// Output a message indicating success.
drupal_set_message('User account created successfully.');

Explanation:

1. Include necessary files and namespaces: Import the required classes and namespaces to use the User entity and the PasswordInterface.
2. Create a new user entity: Use the User::create() method to create a new user entity.
3. Set the username and email: Use the setUsername() and setEmail() methods to set the username and email address for the new user.
4. Set the password: Use the setPassword() method to set the password for the new user. It's important to hash the password using the Drupal password service.
5. Set the status: Use the activate() method to set the status of the user account. You can pass 1 for an active account or 0 for a blocked account.
6. Set additional fields (optional): If you have custom fields in the user entity, you can use the set() method to set their values.
7. Save the user entity: Use the save() method to save the user entity, creating the user account.
8. Output a success message: Display a message to indicate that the user account was created successfully.

Note: This code should be placed in a custom module or a script that is executed within the Drupal environment. Additionally, make sure to adjust the values and customize the code according to your specific requirements.