Laravel: field data changed is not working

I am trying to check if value was changed in a Laravel model, isDirty never executes.

if I remove isDirty Data Updating is working fine only ìsDirty is not working.

public function update(TeacherRequest $request, $id)
{
    $teacher = Teacher::find($id);

    if ($teacher->isDirty($request)) {

        $new_data = $teacher->$request;
        $old_data = $teacher->getOriginal($request);
        return response()->json([
            'msg' => $new_data,
            'msg' => $old_data
        ]);
    }
}

I tried to check only one column as well if it was changed.

One Column check:

if ($teacher->isDirty('efirst')) {

    $new_data = $teacher->efirst;
    $old_data = $teacher->getOriginal('efirst');
    return response()->json([
        'msg' => $new_data,
        'msg' => $old_data
    ]);
}

efirst is the name of the first column and input field.

I am getting nothing as output even if I change data.

via Chebli Mohamed