code: private static function incStat($stat, $inc)
      {
          if ($stat == 'utf8special') {
              $stat = 'bytesSpecial';
          } else {
              $stat = 'bytes'.\ucfirst($stat);
          }
          self::$stats[$stat] += $inc;
      }
docs: Increment statistic
  
  @param string  $stat stat to increment
  @param integer $inc  increment ammount
  
  @return void