problemController2.php

<?php

namespace App\Http\Controllers;

use App\Models\problem;
use Illuminate\Http\Request;
use Models;

class ProblemController extends Controller
{
    /**
     * Display a listing of the resource.
     *
     * @return \Illuminate\Http\Response
     */
    public function index(Request $request)
    {
        $query = problem::query();

        $problemId = $request-> problemId;
        $problemCategory = $request->problemCategory;

        if (!empty($problemId)) {
            $query->Where('problemID', 'like', '%'. $problemId.'%') ;
        }
        if (!empty($problemCategory)) {
            $query->orWhere('problemCategory', 'like', '%'. $problemCategory.'%') ;
        }

        $problems = $query->orderBy('problemId', 'desc')->paginate(10);
        return view('problem.index', [ 'problems' => $problems, 'request' => $request]);
    }
}