How to insert a variable value in the PHP Header?

Question

My intention is that when you delete a bill, it goes back to the index page of notes referring to that work.

Code:

{
    $id = $_POST['id'];
    $ok = $_GET['obra'];
    //Delete do banco:
    $pdo = Banco::conectar();
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $sql = "DELETE FROM notas where id = ?";
    $q = $pdo->prepare($sql);
    $q->execute(array($id));
    Banco::desconectar();
    header('Location: index01.php?obra=' . $ok); 
}