public function getStat($format = 'txt')
 {
     if ($format == 'txt') {
         $pstat = parent::getStat($format);
         $str = "D: ";
         $str .= sprintf("io_w: %s\t", str_pad($this->_stat['io_write'], 3, ' ', STR_PAD_RIGHT));
         $str .= sprintf("io_r: %s\t", str_pad($this->_stat['io_read'], 3, ' ', STR_PAD_RIGHT));
         $str .= sprintf("io_u: %s\t", str_pad($this->_stat['io_unlink'], 3, ' ', STR_PAD_RIGHT));
         $str .= sprintf("io_wt: %s\t", number_format(round($this->_stat['io_write_time'], 3), 2));
         $str .= sprintf("io_rt: %s\t", number_format(round($this->_stat['io_read_time'], 3), 2));
         $str .= sprintf("io_ut: %s\t", number_format(round($this->_stat['io_unlink_time'], 3), 2));
         return $pstat . $str . "\n";
     } else {
         return $this->_stat;
     }
 }
 public function getStat($format = 'txt')
 {
     if ($format == 'txt') {
         $pstat = parent::getStat($format);
         $str = "D: ";
         $str .= sprintf("io_w: %s\t", str_pad($this->_stat['io_write'], 3, ' ', STR_PAD_RIGHT));
         $str .= sprintf("io_r: %s\t", str_pad($this->_stat['io_read'], 3, ' ', STR_PAD_RIGHT));
         $str .= sprintf("io_u: %s\t", str_pad($this->_stat['io_unlink'], 3, ' ', STR_PAD_RIGHT));
         $str .= sprintf("io_wt: %s\t", number_format(round($this->_stat['io_write_time'], 3), 2));
         $str .= sprintf("io_rt: %s\t", number_format(round($this->_stat['io_read_time'], 3), 2));
         $str .= sprintf("io_ut: %s\t", number_format(round($this->_stat['io_unlink_time'], 3), 2));
         $str .= "\n";
         $str .= "D: ";
         $str .= sprintf("err_r: %d\t", $this->_stat['err_file_get_contents']);
         $str .= sprintf("err_w: %d\t", $this->_stat['err_file_put_contents']);
         $str .= sprintf("err_gzinflate: %d\t", $this->_stat['err_gzinflate']);
         $str .= sprintf("err_unserialize: %d\t", $this->_stat['err_unserialize']);
         return $pstat . $str . "\n";
     } else {
         return $this->_stat;
     }
 }