PHP function to make a file size human-readable

Problem: You're working in PHP and you have a file size in bytes. You'd like to make it easier to read.

Answer: This quick function I created. It accepts the byte count and returns a human-readable file size string:

// make file size human-readable
function byte_size($bytes)
{
switch(1)
{
 case ($bytes < pow(2, 10)):    // bytes
  $size = number_format($bytes) . ' B';
  break;
 case ($bytes < pow(2, 20)):
  $size = number_format($bytes / pow(2, 10)) . ' kB';    // kilobytes
  break;
 case ($bytes < pow(2, 30)):
  $size = number_format($bytes / pow(2, 20)) . ' MB';    // megabytes
  break;
 case ($bytes < pow(2,40)):
  $size = number_format($bytes / pow(2,30)) . ' GB';    // gigabytes
  break;
 case ($bytes < pow(2,50)):
  $size = number_format($bytes / pow(2,40)) . ' TB';    // terabytes
  break;
 case ($bytes < pow(2,60)):
  $size = number_format($byes / pow(2,50)) . ' PB';    // pedabytes
  break;
 default:                             // a famous man once said, "a PC will never need more than 640 kB of RAM"
  $size = number_format($bytes) . ' B';
}

return $size;
}