PHP:如何使用另一个类中的参数实例化一个类

class DatabaseConnection
{
    private $host;
    private $username;
    private $password;

    public function __construct($host, $username, $password)
    {
        $this->host = $host;
        $this->username = $username;
        $this->password = $password;
    }

    public function getConnection()
    {
        // 使用 $this->host, $this->username 和 $this->password 建立数据库连接
    }
}

class UserRepository
{
    private $databaseConnection;

    public function __construct(DatabaseConnection $databaseConnection)
    {
        $this->databaseConnection = $databaseConnection;
    }

    public function getAllUsers()
    {
        // 使用 $this->databaseConnection 获取数据库连接，然后执行查询并返回用户列表
    }
}

// 在实例化 UserRepository 时，将已经实例化的 DatabaseConnection 对象传递给它
$databaseConnection = new DatabaseConnection('localhost', 'root', 'password');
$userRepository = new UserRepository($databaseConnection);
$users = $userRepository->getAllUsers();