Indirect modification of overloaded property ModulesProductHttpRequestsCreateProductRequest::$specification has no effect

    foreach($request->specification as $key => $specification){
        $image = null;
        
        if ($specification['icon']) {
            $path_info = pathinfo($_FILES['specification']['name'][$key]['icon']);
            $randomize = rand(111111, 999999);
            $tmpFile = $_FILES['specification']['tmp_name'][$key]['icon'];
            $image = date('mdYHis') . $randomize . '.' . $path_info['extension'];
            $newFile = 'public/fileimage/'.$image;
            $result = move_uploaded_file($tmpFile, $newFile);
            $specification['icon'] = '';
            // dd($specification['icon'] );
            // $request->specification = $specification; 

        }
        // dd($specification);
        $request->specification[$key] = null;
        dd($request->specification[$key]);
        $request->specification[$key] = $specification;
        dd($request->specification[$key]);
    }

its giving me error Indirect modification of overloaded property. I can’t able to update update array value. and not understating the issue.