Store on Data Base serialize array Laravel

i am trying to store in db a serialize array, but I'm not pretty sure how to do that. I need to store "$raport->id_operator = $request->id_operator," as an array in Data Base. The default value for id_operator in db is "a:0:{}". Here si my controller

$arr = array();

    $raport = Raports::find($id);

    $details = [
    $serializedArr = serialize($arr),
    $raport->status = $request->status,
    $raport->approved = $request->approved,
    $raport->modify_user_id = Auth::user()->id,
    $raport->id_operator = $request->id_operator,
    $raport->updated_at = date('Y-m-d H:i:s'),
    ];
    array_push($arr,$details);

    if($raport->save())
    {
        return redirect()->back()->with('success','Kërkesa u dërgua me sukses :)');
    }
    else
    {
        return redirect()->back()->with('error','Kërkesa nuk u dërgua :( ');
    }

and this are the values i want to add every time i edit.

<div class="col-md-4">
 <label>Jep Akses</label>
   <select class="select" name="id_operator" >
      <option value="">Zgjidh operator</option>
        @foreach($users as $user)
     <option value="">            </option>
        @endforeach
   </select>

via User45648