demo/app/Http/Controllers/CommentsController.php

<?php

namespace App\Http\Controllers;

use App\Model\Comment;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Auth;

class CommentsController extends Controller
{
    /**
     * Display a listing of the resource.
     *
     * @return \Illuminate\Http\Response
     */
    public function index()
    {
        //
    }

    /**
     * Show the form for creating a new resource.
     *
     * @return \Illuminate\Http\Response
     */
    public function create()
    {
        //
    }

    /**
     * Store a newly created resource in storage.
     *
     * @param  \Illuminate\Http\Request  $request
     * @return \Illuminate\Http\Response
     */
    public function store(Request $request)
    {
        if (Auth::check()) {
            $comment = Comment::create([
                'body' => $request->input('body'),
                'url' => $request->input('url'),
                'commentable_type' => $request->input('commentable_type'),
                'commentable_id' => $request->input('commentable_id'),
                'user_id' => Auth::user()->id
            ]);

            if ($comment) {
                return back()->with('success', 'Comment created successfully');
            }
        }

        return back()->withInput()->with('errors', 'Error creating new comment');

    }

    /**
     * Display the specified resource.
     *
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function show($id)
    {
        //
    }

    /**
     * Show the form for editing the specified resource.
     *
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function edit($id)
    {
        //
    }

    /**
     * Update the specified resource in storage.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function update(Request $request, $id)
    {
        //
    }

    /**
     * Remove the specified resource from storage.
     *
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function destroy($id)
    {
        //
    }
}