code: public function getPrettySize()
      {
          $size = $this->getLength();
          
          if ($size >= 1073741824) {
              return round($size / 1073741824, 2) . ' GB';
          }
          
          if ($size >= 1048576) {
              return round($size / 1048576, 2) . ' MB';
          }
          
          if ($size >= 1024) {
              return round($size / 1024, 2) . ' kB';
          }
          
          return (string)$size;
      }
docs: Gets the length of file in GB, MB ot kB format
  
  @return string