1 public function getReadableFileSize($retstring=null){ 2   3        $sizes = array(‘byte‘,‘kB‘,‘MB‘,‘GB‘,‘TB‘,‘PB‘,‘EB‘,‘ZB‘,‘YB‘); 4  5        if($retstring == null) 6           $retstring = "%01.2f %s"; 7  8       $lastsizestring = end($sizes); 9 10       foreach($sizes as $sizestring){11           if($this->size<1024)12                 break;13           if($sizestring!=$lastsizestring)14              $this->size/=1024;15      }                        16 17       if($sizestring == $sizes[0])18           $retstring = "%01d %s":19 20       return sprintf($retstring,$this->size,$sizestring);21 }