framework/rest/UpdateAction.php
public function run($id)
    {
        /* @var $model ActiveRecord */
        $model = $this->findModel($id);

        if ($this->checkAccess) {
            call_user_func($this->checkAccess, $this->id, $model);
        }

        $model->scenario = $this->scenario;
        $model->load(Yii::$app->getRequest()->getBodyParams(), '');
        if ($model->save() === false && !$model->hasErrors()) {
            throw new ServerErrorHttpException('Failed to update the object for unknown reason.');
        }

        return $model;
    }
public function run($id)
    {
        /* @var $model ActiveRecord */
        $model = $this->findModel($id);

        if ($this->checkAccess) {
            call_user_func($this->checkAccess, $this->id, $model);
        }

        $model->scenario = $this->scenario;
        $model->load(Yii::$app->getRequest()->getBodyParams(), '');
        if ($model->save() === false && !$model->hasErrors()) {
            throw new ServerErrorHttpException('Failed to update the object for unknown reason.');
        }

        return $model;
    }
Updates an existing model.
@param string $id the primary key of the model.
@return \yii\db\ActiveRecordInterface the model being updated
@throws ServerErrorHttpException if there is any error when updating the model