问如何将选择列表的整数值传递给控制器？

EN

<form action="../media" method="post" enctype="multipart/form-data">
{{csrf_field()}}
title: <input type="text" name="title">
<br> <br>
type:
<input type="radio" name="type" value="voice" checked>Voice<br>
<input type="radio" name="type" value="video">Video<br>
<br> <br>
link: <input type="file" name="link">
<br><br>
course:
<select name="$courses" >
    @foreach($courses as $course)
        <option value="{{$course->id}}">
            {{$course->title}}
        </option>
    @endforeach
</select>
<br><br>
<input type="submit">

 public function store(Request $request)
{
    //dd($request->all());
    $media=new Media();
    $media->title=$request->title;
    $media->type=$request->type;
    $media->course_id=(int)($request->courses);
    $media->save();
    $format=$request->file('link')->getClientOriginalExtension();
    $size=$request->file('link')->getSize();
    $name=$request->type.'-'.$media->id.'.'.$format;
    $request->file('link')->move(public_path('medias'),$name);
    $media->link= $name;
    $media->format=$format;
    $media->size=$size;
    $media->save();
    return back();
}

 public function create()
{
    $courses=Course::all();
    return view('Admin.Media.create',compact('courses'));
}