SQLSTATE [42S22]：找不到列：1054'字段列表'中的未知列'firstName'

I'm trying to log data into my database, but I keep getting the following error:

SQLSTATE[42S22]: Column not found: 1054 Unknown column 'firstName' in 'field list'

I have done research and still haven't found the answer. Do I have any unseen mistakes in my code? Am I doing something wrong? I don't see why I'm getting this error, my database does have a column called firstName. Thanks.

$db = new PDO('mysql:host=localhost;dbname=bord','root','root');
  $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
  $sql = "INSERT INTO users (firstName, lastName, password, email, code, active, month) VALUES (
    :firstName, :lastName, :password, :email, :code, :active, :month
  )";
  $statement = $db->prepare($sql);
  $statement->bindParam(':firstName', $firstName);
  $statement->bindParam(':lastName', $lastName);
  $statement->bindParam(':password', $password);
  $statement->bindParam(':email', $email);
  $statement->bindParam(':code', $code);
  $statement->bindParam(':active', $active);
  $statement->bindParam(':month', $month);

  $firstName = 'Mitchell';
  $lastName = "Sanders";
  $password = "password";
  $email = "msandy@fakemail.com";
  $code = 12345;
  $active = 0;
  $month = date("F");
  $statement->execute();