Code

$sql = "INSERT INTO `users` (first_name, last_name, email, phone, username, password, active, level, created_at, updated_at) VALUES (:first_name, :last_name, :email, :phone, :username, :password, :active, :level, :created_at, :updated_at)";
$this->db->insert($sql, array(
    ":first_name" => $user->FirstName(),
    ":last_name" => $user->LastName(),
    ":email" => $user->Email(),
    ":phone" => $user->Phone(),
    ":username" => $user->Username(),
    ":password" => $user->Password(),
    ":active" => $user->Active(),
    ":level" => $user->Level(),
    ":created_at" => time(),
     ":updated_at" => time()
));