我有一个问题，每当我更新一个文件，它总是会错误出未知变量[Fname]这是我的控制器中的更新函数

public function update(Request $request, $PaperID)
    {
        $request->validate([
            'PaperTitle' => 'required',
            'PaperType' => 'required',
            'file' => [
                'required',
                File::types('pdf')
                    ->max(12 * 1024),
            ],
        ]);

        $paper=Papers::find($PaperID);
        

        $file=$request->file;

        $filename=time().'.'.$file->getClientOriginalExtension();
                $request->file->move('assets', $filename);
                $paper->file=$filename;

            $paper->PaperTitle=$request->PaperTitle;
            $paper->PaperType=$request->PaperType;
            $paper->College=$request->College;
            $paper->DateCompleted=$request->DateCompleted;
            $paper->ContentAdviser=$request->ContentAdviser;
            
            $paper->update();

            $input = $request->all();

            if(count($input['Fname']) > 0){
                for($i = 0 ; $i < count($input['Fname']) ; $i++){
                    
    
                    $author->Fname = $input['Fname'][$i];
                    $author->Lname = $input['Lname'][$i];
                    $author->update();
                }
            }

            return redirect()->back()->with('success','File has been updated.');

    }

存储工作正常，但更新不如何解决这个问题？我希望这两个论文和作者表将更新论文更新好，但作者不