Check user count to prevent more than one registered user

app/Http/Controllers/UserController.php

@@ -5,6 +5,7 @@ namespace App\Http\Controllers;
 use App\User;
 use Validator;
 use Illuminate\Http\Request;
+use Illuminate\Support\Facades\DB;
 use App\Http\Controllers\Controller;
 use Illuminate\Support\Facades\Auth;
 
@@ -56,6 +57,20 @@ class UserController extends Controller
     }
 
 
+    /**
+     * check if a user exists
+     * @param  Request $request [description]
+     * @return json
+     */
+    public function checkUser()
+    {
+
+        $count = DB::table('users')->count();
+
+        return response()->json(['userCount' => $count], 200);
+    }
+
+
     /**
      * register new user
      * @param  Request $request [description]
@@ -63,6 +78,14 @@ class UserController extends Controller
      */
     public function register(Request $request)
     {
+
+        // check if a user already exists
+        $count = DB::table('users')->count();
+
+        if( $count > 0 ) {
+            return response()->json(['error' => __('already_one_user_registered')], 400);
+        }
+
         $validator = Validator::make($request->all(), [
             'name' => 'required',
             'email' => 'required|email',