human readable file size

Try something like this:

function humanFileSize($size,$unit="") {
  if( (!$unit && $size >= 1<<30) || $unit == "GB")
    return number_format($size/(1<<30),2)."GB";
  if( (!$unit && $size >= 1<<20) || $unit == "MB")
    return number_format($size/(1<<20),2)."MB";
  if( (!$unit && $size >= 1<<10) || $unit == "KB")
    return number_format($size/(1<<10),2)."KB";
  return number_format($size)." bytes";
}