Custom Login Updating Details In Laravel 5.4

I am trying to change or update user details while custom login. i have a table named student_table. there has some student details. With mail address and password i can login in dashboard. but in dashboard there is a page named setting page. with setting page i want to update phone, address and password number. but while trying or i click that page, the page is showing with blank page. the image is below, anything error or suggestion for updating controller code?

My controller code

public function student_settings()

    {
        $student_id = Session::get('student_id');
        $viewData = saveStudent::select('*') 
        -> where('student_id', $student_id)
        -> first();

       return view('student_settings', compact('viewData'));


    }

View page Code

@extends('student_layout')

@section('content')

   <div class="content-wrapper">
          <div class="row">
            <div class="col-12 col-lg-6 grid-margin">
                  <div class="card">
                      <div class="card-body">
                          <h2 class="card-title">Update Your Details

 @if(count($errors) > 0)
@foreach($errors ->all() as $error)

              <div class="alert alert-danger"> </div>

          @endforeach
          @endif


      @if(count($viewData)> 0)

  @foreach($viewData -> all() as $singleData)           

     <form class="forms-sample" method="post" action="">

        



                              <div class="form-group">

                                  <label for="exampleInputEmail6">Student Phone</label>

                                  <input type="text" id="exampleInputEmail6" class="form-control p-input" name="student_phone" placeholder="Enter PhoneNumber" value="">

                              </div>

                              <div class="form-group">

                                  <label for="exampleInputEmail7">Student Address</label>

                                  <input type="text" id="exampleInputEmail7" class="form-control p-input" name="student_address" placeholder="Enter Address" value="">
                              </div>

                               <div class="form-group">

                                  <label for="exampleInputEmail7">Student Password</label>

                                  <input type="password" id="exampleInputEmail7" class="form-control p-input" name="student_address" placeholder="Enter Address" value="">
                              </div>



                              <button type="submit" class="btn btn-success">Update</button>
                          </form>
                          @endforeach
                          @endif
                      </div>
                  </div>
              </div>
          </div>

        </div>

@endsection

via Chebli Mohamed