Yii2 Kartik editable widget - ajax

Question

I have a problem with my Kartik input text editable widget. It affected on the tema column in my table. The problem is, on my chrome developer tool it returns an "Internal server error" on the AJAX processing. The response header's content is : Content-Type: application/json; charset=UTF-8 but the connection remains close. Is there anything wrong with my code? Note : the initial value of the editable's label is NOT SET (which should be the value of "tema" column retrieved from my $model->tema). The model name is Home.
My HomeController :
public function actionIndex()
{
$searchModel = new HomeSearch();
$dataProvider = $searchModel->search(Yii::$app->request->queryParams);
$model = new Home;
// Check if there is an Editable ajax request
if (isset($_POST['hasEditable'])) {
// use Yii's response format to encode output as JSON
\Yii::$app->response->format = \yii\web\Response::FORMAT_JSON;
$temaId=Yii::$app->request->post('editableKey');
$query= Home::find()->where(['id'=> $temaId])->one();
// read your posted model attributes
if ($model->load($_POST)) {
// read or convert your posted information
$value = $query->tema;
$value->save();
// return JSON encoded output in the below format
return ['output'=>$value, 'message'=>''];
// alternatively you can return a validation error
// return ['output'=>'', 'message'=>'Validation error'];
} else {
// else if nothing to do always return an empty JSON encoded output
return ['output'=>'', 'message'=>''];
}
};
return $this->render('index', [
'searchModel' => $searchModel,
'dataProvider' => $dataProvider,
'model'=>$model,
]);
}
The view file
use kartik\editable\Editable;
<?php
echo Editable::widget([
'model' => $model,
'attribute' => 'tema',
'type' => 'post',
'value'=>$model->tema,
'header'=>'tema',
'size'=> 'lg',
'inputType' => Editable::INPUT_TEXT,
'editableValueOptions' => ['class' => 'text-success h3']
]);
?>
Please help. Have spent two days on this. Thanks!