I am using codeigniter with shield and i have a edit userpage, in the controller I have

 public function update($id)
  {
    $users = auth()->getProvider();
    $user = $users->findById($id);        

    if ($this->validate($rules))
    {
        $user->fill([
            'username' => $this->request->getPost('username'),
            'email' => $this->request->getPost('email'),
            'status' => $this->request->getPost('isBanned')
         ]);

        $users->save($user);

            return redirect()->to("admin/dashboard/manage-users")
                ->with("message", "User updated.");
        }

    return redirect()->back()
        ->with("errors", $this->validator->getErrors())
        ->withInput();
}

In the data base there is a field called status by default it is Null

I want to change the status to Banned if checked if unchecked set back to null
The only way I have been able to get this to semi work is the following

<div>
    <input type="checkbox" id="isBanned" name="isBanned" value="banned" <?= set_checkbox('status', 'banned') ?>>
    <input type="checkbox" id="isBanned" name="isBanned" value="NULL" <?= set_checkbox('status', 'NULL') ?>>
    <label for="isBanned">Banned</label>
</div>

I would like to be able to use only 1 checkbox on if the user is banned it stays checked until i uncheck it