Trying to get the hang of PDO

Hi Guys!

Lisa's back with her super dumb question time!

I'm trying to get the hang of PDO, and I understand that it'll be easier for my DB Connections in the future, but there are just some (probably basic) things that I'm getting stuck on.

Let's say I have this in my class

  private $_db = new PDO;
  $network_name;
  $username;
  $password;
  $profile_url;

  __constructor($client_id, $network)
  {
    $_db = PDO(connection_string_info_you_dont_get_to_see);
    $query = "SELECT * FROM social_media ";
    $query .= "WHERE client_id = " . $client_id . " AND network_name = " . $network . " ";
    $query .= "LIMIT 0, 1;";

    try
    {
      $result = $_db->query($query);
      
      $result->bindColumn('username', $username);
      $result->bindColumn('password', $password);
      $result->bindColumn('profile_url', $profile_url);
      $network_name = $network;
      
      while ($row = $result->fetch(PDO_FETCH_BOUND))
      {
        //Stuff I haven't thought of yet goes here
      }
    }
    catch(PDOException $e)
    {
      echo $e->getMessage();
    }
  }

The goal is to 1) pull the customer's login information for $network out of our database and display it for them on the page (we really try and dumb things down for them), and 2) set $username, $password, and $profile_url, which are data members for my class, with their initial values.

Would the values bound $username, $password, and $profile_url persist after the while loop has ended? Or because of the use of bindColumn, would the values be trashed? Or do I even need the while loop at all? Some of the things I'm reading seem to conflict as to whether or not I need it.

Thanks again!