/** ajax module for get statistics regarding date range  */
 public static function ajax_get_daterange()
 {
     $general_settings = get_option('ws_main_option', array());
     if (!class_exists('Mailin')) {
         require_once 'includes/mailin.php';
     }
     $mailin = new Mailin(WC_Sendinblue::sendinblue_api_url, $general_settings['access_key']);
     $begin = new DateTime($_POST['begin']);
     //Date
     $end = new DateTime($_POST['end']);
     if ($begin == $end) {
         $begin = $begin->modify('+1 day');
         $end = $end->modify('+2 day');
     } else {
         $begin = $begin->modify('+1 day');
         $end = $end->modify('+1 day');
     }
     $begin = $begin->format("Y-m-d");
     $end = $end->format("Y-m-d");
     $statistics = WC_Sendinblue::get_statistics($mailin, $begin, $end);
     echo json_encode($statistics);
     die;
 }