/**
  * @param int $page
  * @param int $end
  * @param bool $allRecords
  */
 public static function calculate($page, $end = 20, $allRecords = false)
 {
     self::$page = intval($page);
     self::$countPage = ceil($allRecords / $end);
     self::$end = $end;
     self::$allRecords = $allRecords;
     if (self::$page <= 1 or self::$page > self::$countPage) {
         self::$page = 1;
         self::$start = 0;
     } else {
         self::$start = (self::$page - 1) * self::$end;
     }
 }