php 文件大小计算转换

　　/**
     * [tosize description]
     * @Author:XuXianGang
     * @Method: 文件格式大小
     * @DateTime:2021-09-02T15:44:07+0800
     * @param[type] $file_size [文件大小]
     * @return[type]            [description]
     */
    function tosize($file_size){
        $file_size = $file_size-1;
        if ($file_size >= 1099511627776) 
            $show_filesize = number_format(($file_size / 1099511627776),2) . " TB";
        elseif ($file_size >= 1073741824) 
            $show_filesize = number_format(($file_size / 1073741824),2) . " GB";
        elseif ($file_size >= 1048576) 
            $show_filesize = number_format(($file_size / 1048576),2) . " MB";
        elseif ($file_size >= 1024) 
            $show_filesize = number_format(($file_size / 1024),2) . " KB";
        elseif ($file_size > 0) 
            $show_filesize = $file_size . " b";
        elseif ($file_size == 0 || $file_size == -1) 
            $show_filesize = "0 b";
        return $show_filesize;
    }