Laravel isdirty method Mass Assignment

My Code is saving data of only one field(efirst) if it's changed by isDirty() method, and it's working correctly. how can i achieve same result if i have 10 fields `without writing each field name.

`

Controller:

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

      $teacher->efirst=$request->efirst;
    if ($teacher->isDirty()) {
      $new_data = $teacher->efirst;
      $old_data = $teacher->getOriginal('efirst');

    if($teacher->save()){

  $teacher->update($request->except('qual_id','id','profile_pic'));

      DB::table('teacher_logs')->insert(
      ['user_id' => $user->id,
       'teacher_id' => $teacher->id,
       'old_value' => $old_data,
       'new_value' => $new_data,
     ]);
    }
  }}

via Chebli Mohamed