php - file size not shown before download start

Here is my code in php : **Download worked but file size not showed size **

$infofile="sample.rar";
header("Content-Description:File Transfer");
header("Content-Type:application/x-rar");
header("Content-Lenght:".(string)filesize($infofile));
header("Content-Disposition:attachment;filename=sample_filename_for_dowload.rar");
header("Expires:0");
header("Cache-Control:must-revalidate,post-check=0,pre=check=0");
header("Progma:public");
ob_clean();
flush();
readfile($infofile);
Copy code