function get_size($s,$u='B',$p=1){
  $us = array('B'=>'K','K'=>'M','M'=>'G','G'=>'T');
  return (($u!=='B')&&(!isset($us[$u]))||($s<1024))?(number_format($s,$p)." $u"):(get_size($s/1024,$us[$u],$p));
}