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

Question

我正在尝试将数据记录到我的数据库中，但我一直收到以下错误：

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

我做过研究但仍未找到答案。我的代码中是否有任何看不见的错误？难道我做错了什么？我不明白为什么我收到此错误，我的数据库确实有一个名为firstName的列。感谢。

$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();