Controller

app\Http\Controllers\TodoController.php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use App\Posts;

class TodoController extends Controller
{
    public function index()
    {
        return view('todo.index');
    }

    public function update(Request $request)
    {
        // $posts = new Posts();
        // $posts->post_name = $request->post_name;
        // $posts->save();

        // $obj = Posts::create([
        //     'post_name' => $request->post_name
        // ]);

        $obj = Posts::create($request->all());
        
        return $obj;
    }
}

為什麼要這樣呢？Posts::create($request->all());

因為如果你的表單的input有100個，你只要寫這一行，就解決了

就不用在接參數時，再複製貼上100次的input的name，快速，少寫代碼，就是它的用意