Get ODBC Driver Name with PDO

Question

Here is my connection string (set elsewhere):

$dns = "odbc:Driver=MDBTools;DBQ=/home/mbi-admin/scripts/RE/ConstituentData.MDB;"

Here is my code

function  InitializeDB($dsn, $user, $pass)
{
echo "************** \n";
  //$dsn = "mysql:host=$host;dbname=$db;charset=$charset";
  $options = [
    PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
    PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
    PDO::ATTR_EMULATE_PREPARES   => false,
  ];
  /*
  echo "***DSN: $dsn \n";
  echo "***User: $user \n";
  echo "***Pass: $pass \n";
  echo "********Option: " ;
  print_r($options);
  echo " \n";
  */
  try {
    $pdo = new PDO($dsn, $user, $pass, $options);
      return $pdo;
  } catch (\PDOException $e) {
      throw new \PDOException($e->getMessage(), (int)$e->getCode());
  }
}

Later on in my code I want to be able to determine that this is MDBTools, however when I try to do

getAttribute(PDO::ATTR_DRIVER_NAME)

I only get odbc. How do I find the driver name of an open connection?