public function actionIndex()
{
$searchModel = new CashbookSearch();
$searchModel->start_date = date('Y-m-01');
// get start date
$searchModel->end_date = date("Y-m-t");
// get end date
$dataProvider = $searchModel->search(Yii::$app->request->queryParams);
return $this->render('index', ['searchModel' => $searchModel, 'dataProvider' => $dataProvider]);
}