查询结果导致PDOStatement错误

Question

I am getting a fairly obvious sounding error in my PHP code: fatal error: Cannot use object of type PDOStatement as array in. But looking at my code, I don't understand why. I have these 2 lines of code:

$orderInfo = get_Order_By_Id($order_id);
echo "<br>".$orderInfo['XYZABC']."-<br>";

Which is calling this function:

function get_Order_By_Id($abc){
  global $db;
  $query = "SELECT * FROM  . . . . WHERE id = ".$abc;
  $results = $db->query($query)->fetch(PDO::FETCH_ASSOC);
  return $results;
}

So I am executing a statement and returning it like I've done a million times…and I'm getting this error? Why? I am executing the statement and trying to the results--why is that throwing this error?