Formats a file size (Bytes) into something readable (KB, MB, ...)

file_format_file_size.php

<?php
function __format_file_fize_size( $size, $display_bytes=false ) {
  if( $size < 1024 )
    $filesize = $size . ' bytes';
  elseif( $size >= 1024 && $size < 1048576 )
    $filesize = round( $size/1024, 2 ) . ' KB';

  elseif( $size >= 1048576 )
    $filesize = round( $size/1048576, 2 ) . ' MB';

  if( $size >= 1024 && $display_bytes )
    $filesize = $filesize . ' (' . $size . ' bytes)';

  return $filesize;
}