问在Laravel类别中显示帖子时出现问题

EN

    namespace App\Http\Controllers;

use Illuminate\Http\Request;
use Illuminate\Support\Facades\DB;

class categoryController extends Controller
{
    public function index($category_name)
    {
        $category_name_exist = DB::table("category")->where('cat_name', $category_name)->exists();
        if ($category_name_exist) {
            $category_name = DB::table("category")->where('cat_name', $category_name)->first();
            return view('category/index', ['category' => $category_name]);
        } else {
            return view('404');
        }
    }
}

Route::get('category/{category_name}','categoryController@index');

    @extends('layout/main')

@section('title') Category @stop

@section('content')
<section class="page-title-section section-padding">
    <div class="container">
        <div class="row">
            <div class="col-md-12 ">
                <h2 class="page-tagline text-center">Now view the category domains</h2>
                <h1 class="page-title text-center xl">{{$category->cat_name}}</h1>
            </div>
        </div>
    </div>
</section>

@stop

    $get_domain_cat_id = $_GET['id'];
$query_cat = $conn->query("select * from category WHERE cat_id='$get_domain_cat_id'");
if ($query_cat->rowCount() == 0) {
    header("location:$url");
}
$fetchall = $query_cat->fetchObject();
$query_cats2 = $conn->query("select * from domains WHERE  FIND_IN_SET('$get_domain_cat_id',category)");
$fetchalls2 = $query_cats2->fetchall();