code: private function sizeToBytes($sizeStr)
      {
          switch (substr($sizeStr, -1)) {
              case 'M':
              case 'm':
                  return (int) $sizeStr * 1048576;
              case 'K':
              case 'k':
                  return (int) $sizeStr * 1024;
              case 'G':
              case 'g':
                  return (int) $sizeStr * 1073741824;
              default:
                  return (int) $sizeStr;
          }
      }
docs: Converts php.ini style size to bytes.
  
  @param string $sizeStr $sizeStr
  @return int