laravel 5.3 $request->submit

How to check is form was submitted?

view:

 {!! Form::open(['method' => 'GET', 'action' => 'JobController@index']) !!}

     <div class="form-group">
     {!! Form::label('keywords','Keywords' ) !!}
     {!! Form::text('keywords', null, array('class' => 'form-control')) !!}
      </div>

    {!! Form::submit('submit', array('class' => 'btn btn-primary form-control ')) !!}
    {!! Form::close() !!}

Controller:

public function index(Request $request) {
 // if(!empty($request->keywords)) {
      //   
        //   $search = Post::where("keywords","LIKE","%{$request->keywords}%")
          //           ->paginate(10);        
    // }


     if(!empty($request->submit)) {

       $search = Post::where("keywords","LIKE","%{$request->keywords}%")
                 ->paginate(10);

     }

   }

$request->keywords is working fine. $request->submit shows nothing. Is this constuction do not work in Laravel? Thanks!

via Chebli Mohamed