請問這樣的關聯性要如何使用Eloquent
我在Program Model底下是這樣做的

class Program extends Model {
    ......
    public function operations() {
        return $this->belongsToMany(Operation::class, config('permission.table_names')['permissions'], 'operation_id', 'program_id')
        ->withTimestamps();
    }
}

在Operation Model 底下是這樣做的

class Operation extends Model {
    ......
    public function programs() {
        return $this->belongsToMany(Program::class, config('permission.table_names')['permissions'], 'operation_id', 'program_id')
        ->withTimestamps();
    }
}

在OperationController裡這樣做

public function store(Request $request) {
    $this->validate($request, [
        'opr_id'=>'required|max:120|unique:operations',
        'desc'=>'required|max:120'
    ]);

    $opr_id = $request['opr_id'];
    $operation = new Operation();
    $operation->opr_id = $opr_id;
    $operation->desc = $request['desc'];

    $operation->save();

    $programs = $request['programs'];
    $operation = Operation::where('opr_id', '=', $opr_id)->first();
    if(is_array($programs)) {
        $operation->programs()->sync([1]);
    } else {
        $operation->programs()->detach();
    }

    return redirect()->route('operations.index')
        ->with('flash_message',trans('messages.operation_successfully_added',['name'=> $opr_id]));
}

public function update(Request $request, $id) {
    $operation = Operation::findOrFail($id);

    $this->validate($request, [
        'opr_id'=>'required|max:120',
        'desc'=>'required|max:120'
    ]);

    $input = $request->only('opr_id','desc');
    $operation->fill($input)->save();

    $programs = $request['programs'];
    $programs = array_map('intval', $programs);
    $operation->programs()->detach();
    if(is_array($programs)) {
        $operation->programs()->sync($programs);
    }

    return redirect()->route('operations.index')
        ->with('flash_message',trans('messages.operation_successfully_updated',['name'=> $input['opr_id']]));
}

store 成功的新增了permissions，但是update時卻是沒有變化的，不知問題出在哪兒
是否是因為foreign key的關係而無法正常運作？我又該如何修改？

第一次提問+剛學習laravel，若有敘述不清的部分，請多包涵