不要在数据透视表中插入值（Laravel 5.8）

Question

I have three table Students ,Subject and Pivot table name 'student_subject' ,when using attach(1) work it (Insert data in pivot table) .

but when using attach($request -> subject) dont work

why ? i dont now

Model :

class Student

    class Student extends Model
{


    protected $fillable=['user_id','FullName','age','address','father_ID','photo_id','class_id'];

    public function subject(){
        return $this->belongsToMany(Subject::class);
    }

    public function classes(){
        return $this->belongsTo('App\classes','class_id');
    }
    public function user(){
        return $this->belongsTo('App\User');
    }
    public function photo(){
        return $this->belongsTo('App\photo');
    }


    //
}

class Subject :

    class Subject extends Model
{
    protected $fillable = ['name','user_id'];
    //

    public function student()
    {
        return $this->belongsToMany(Student::class);

    }
}

Student Controller

      public function store(Request $request)
{
    $input =$request->all();
    $user  =Auth::user();


   if ($file = $request->file('photo_id')){
       $name = time().$file->getClientOriginalName();
       $file->move('images',$name);
       $photo = photo::create(['file'=>$name]);

   $input['photo_id']=$photo->id;

   }
   $student = $user->student()->create($input);

   // $student = $user->student()->create($input);

    $request['student_id'] = $request->id;
    $student->subject()->attach(1);
    dd($student);
    return redirect('admin/students');

Create View :

    @foreach($subjects as $subject)
    <tr>
        <td>

            <div class="form-group" {‌{}}>
                {!! Form::label('name', $subject) !!}
                {!! Form::checkbox('name',$subject,false,                ['class'=>'form-control'])!!}
            </div>

        </td>
    </tr>
@endforeach

Pivot table 'student_subject'

    public function up()
{
    Schema::create('student_subject', function (Blueprint $table) {
        $table->bigIncrements('id');
        $table->unsignedBigInteger('student_id');
        $table->unsignedBigInteger('subject_id');

        // $table->foreign('student_id')->references('id')->on('students');
        $table->foreign('student_id')->references('id')->on('students');

        $table->foreign('subject_id')->references('id')->on('subjects');
    });
}                                

Answer 1

If you have multiple checkboxes you should set name of checkbox as an array name[].

Form::checkbox('name[]', $subject, false);

Then you can get $request->name as an array

$subjects = $request->input('name');
foreach($subjects as $subject){
 $student->subject()->attach($subject);
}

Check this question Laravel - Store multiple checkbox form values in database