yii2 editable internal server error -

i have gangguan model, have id_registrasi (not pk) in gangguan model, want edit id_registrasi in gridview using editable, pop windows give error message "internal server error" when refresh page (f5), column has successful changed. , problem cant handle error. .. controller

if(yii::$app->request->post('haseditable')){         $id = yii::$app->request->post('editablekey');         $model1 = $this->findmodel($id);         $posted = current($_post['gangguan']);             $model1->id_registrasi = $posted['id_registrasi'];             $model1->save(false);           $output =  $model1->id_registrasi;          $out = json::encode(['output'=>$output, 'message'=>'']);         echo $out;          return; } 

and column

[ 'class' => 'kartik\grid\editablecolumn', 'attribute'=>'id_registrasi', 'halign' => 'top', 'valign' => 'middle', 'width'=>'100px', 'headeroptions' => ['class' => 'kv-sticky-column'], 'contentoptions' => ['class' => 'kv-sticky-column'],           'footeroptions' => ['class' => 'kv-sticky-column'], 'pagesummary' => true, ], 

use following in controller , should ok then.

use yii\helpers\json;