一个好的关于计算文件大小，及使其便于阅读的方法(php)

 public function getReadableFileSize($retstring=null){

        $sizes = array('byte','kB','MB','GB','TB','PB','EB','ZB','YB');

        if($retstring == null)
           $retstring = "%01.2f %s";

       $lastsizestring = end($sizes);

       foreach($sizes as $sizestring){
           if($this->size<1024)
                 break;
           if($sizestring!=$lastsizestring)
              $this->size/=1024;
      }                        

       if($sizestring == $sizes[0])
           $retstring = "%01d %s":

       return sprintf($retstring,$this->size,$sizestring);
 }