Doubt about data return in PHP POO

Question

I’m learning about object-oriented programming in PHP, classes, hierarchies and so on. Reading a few topics right here on stackoverflow I found the solution to my problem with the user control class, but I got a question regarding this.

The class would be:

class UserService
{
protected $_email;    // using protected so they can be accessed
protected $_password; // and overidden if necessary
protected $_user;     // stores the user data

public function __construct($email, $password) 
{
   $this->_email = $email;
   $this->_password = $password;
}
public function login()
{
    $user = $this->_checkCredentials();
    if ($user) {
        $this->_user = $user; // store it so it can be accessed later
        $_SESSION['user_id'] = $user['id'];
        return $user['id'];
    }
    return false;
}

protected function _checkCredentials()
{

    /* Faz a rotina para verificar se o usuário está no banco de dados*/
    /* e se a senha confere */

    /* Se OK retorna os dados do usuário, se não, retorna false */

}   
}

I am in doubt on how to use this class if I want to return only the username for example.

To log in the user I understood, would be:

session_start();
include("class.user.php");

$user = new UserService($_POST['email'], $_POST['pass']);

But if I want to return only the name (or some other data) of the user already logged in, without having to pass the parameters "email" and "password" again?

I would have to create a function within the class for me to pass the user ID stored in $_SESSION and the class would return the data, but I would have to instantiate the class using "new" again?

For example, in the class, add:

public function getUserName($uID)
{
   /* Verifica se o usuário está logado e busca o nome no DB */       
}

And in the main file (considering that the user has already been previously logged in):

session_start();
include("class.user.php");

$user = new UserService();

$userName = $user->getUserName($_SESSION['user_id']);

echo $userName;

That is correct?

EDIT: This class is just a draft of what I intend to do, I understand that it is necessary to correct some excerpts, sanitize the fields, encrypt the password and etc, this is just to demonstrate my doubt.

Answer 1

All you have to do is set session_start() in the __construct, case after login you already put the $_SESSION['nome'] then I’d be like this:

  public function getUserName()
  {
    return $_SESSION['nome'];
  }