laravel insert multiple data ​to the database

I want to save the data to the database. By saving through a dynamic form many row, but what I tried was not working

Please introduce me, I am a beginner.

Form :

      <form class="form-ajax" action="/standard_sub" method="POST" name="add_name" id="add_name">  
    @csrf()
                            <td><input type="text" name="standard_sub_code[]" placeholder="Enter your Subcode" class="form-control name_list" /></td>  
                            <td><input type="text" name="standard_sub_name[]" placeholder="Enter your Subname" class="form-control code_list" /></td>  
                            <td>
                                <select class="form-control">
                                    <option value="all">
                                        ทั้งหมด
                                    </option>
                                @foreach($standard_main as $index => $row)
                                    <option name="standard_main_id[]" value="{{$row->standard_main_id}}">
                                        {{$row->standard_main_code}} {{$row->standard_main_name}}
                                    </option>
                                @endforeach
                                </select>
                            </td>  
                            <td><button type="button" name="add" id="add" class="btn btn-success">Add More</button></td>  

            </div>  
        </form>  

Controller :

     public function store(Request $request)
{
    $standard_sub_code = $request->get('standard_sub_code');
    $standard_sub_name = $request->get('standard_sub_name');
    $standard_main_id = $request->get('standard_main_id');


    if(is_array($standard_sub_code) && is_array($standard_sub_name) && is_array($standard_main_id))        
    {
        DB::table('standard_sub')->insert([
            'standard_sub_code' =>$standard_sub_code,
            'standard_sub_name' =>$standard_sub_name,
            'standard_main_id' =>$standard_main_id,
            'created_at' =>date('Y-m-d H:i:s'),
        ]);

}