Returns units based on bytes

bytesize.php

function ByteSize($size)
{
    static $unit = array('B', 'kB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB');
    $size/=(pow(1024,($idx=floor(log($size)/log(1024)))));
    return number_format($size,2).$unit[$idx];
}