gistfile1.aw

<?php
function humanReadableOctets($octets) { 
    $units = array('B', 'kB', 'MB', 'GB', 'TB'); 

    for ($i = 0, $size =$octets; $size>1024; $size=$size/1024) 
        $i++; 

    return number_format($size, 2) . ' ' . $units[min($i, count($units) -1 )]; 
} 


echo humanReadableOctets(1000000000000999);