PHP strongly typed arrays with a required length of one

UserRepository.php

<?php

public function save(User $user, User ...$users): void
{
    $users[] = $user;
  
    foreach ($users as $user) {
        // Save the user
    }
}

$users = [
    new User('Tijmen'),
    new User('Paul'),
    new User('Bart')
];

save(...$users);