如果要驗證輸入的文字框，最少需要輸入5個字元，可以用validate的這個方法

Controller

app\Http\Controllers\TodoController.php

namespace App\Http\Controllers;

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

class TodoController extends Controller
{
    public function index()
    {
        $posts = Posts::all();

        return view('todo.index', [
            'posts' => $posts
        ]);
    }

    public function add(Request $request)
    {
        $validatedData = $request->validate([
            'post_name' => 'required|min:5',
        ]);

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

        return redirect("/todo");
    }

    public function destroy(Request $request, Posts $posts)
    {
        $posts->delete();
        return redirect("/todo");
    }
}

關鍵就在這一行

$validatedData = $request->validate([
            'post_name' => 'required|min:5',
        ]);

Route

routes\web.php

Route::get('/todo', 'TodoController@index');
Route::post('/todo', 'TodoController@add');
Route::delete('/todo/{posts}', 'TodoController@destroy');

View

resources\views\todo\index.blade.php

錯誤處理：要顯示錯誤訊息的處理方法

@if ($errors->any())
    

        

            @foreach ($errors->all() as $error)
                
{{ $error }}
            @endforeach
        
    
@endif

範例圖如下：