Symfony \ Component \ Debug \ Exception \ FatalThrowableError (E_ERROR) . Class ‘App\Http\Controllers\DB’ Not Found.

“Symfony \ Component \ Debug \ Exception \ FatalThrowableError (E_ERROR) . Class ‘App\Http\Controllers\DB’ Not Found ” error might occored
because of use DB;  missing in your controller.

So add controller class use in your controller.
So the top of the controller will look like as follows.

<?php
namespace App\Http\Controllers;
use Illuminate\Http\Request;use Illuminate\Database\Eloquent\Model;use App\User;use DB;