malformed header from script. Bad header=1: index.php

Question

I have a website which is a few years old now, it basically offers downloads.

Anyway since moving server people can not download files because its now giving a error 500 error and in the log files it is bringing this error:

malformed header from script. Bad header=1: index.php

The only code which is related to this which I can see anyway is this:

// Echo $productOptionDetails->file;                
$file = DOWNLOAD_FOLDER. '/'. $productOptionDetailEntity->file;

    if (file_exists($file)) {

        header('Content-Description: File Transfer');
        header('Content-Type: application/octet-stream');
        header('Content-Disposition: attachment; filename='.basename($file));
        header('Content-Transfer-Encoding: binary');
        header('Expires: 0');
        header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
        header('Pragma: public');
        header('Content-Length: ' . filesize($file) + 1);
        ob_clean();
        flush();
        readfile($file);
        exit;
    }

Now if I just output:

// Echo $productOptionDetails->file;                
$file = DOWNLOAD_FOLDER. '/'. $productOptionDetailEntity->file;

if (file_exists($file)) {
   readfile($file);
   exit;
}

It outputs lots of encrypted text so its obviously reading something.

What I have read is that the headers are incorrect but after reading loads of content in php.net as well as other websites this looks fine.

Can anyone give a shout on why I am getting these errors?

Thanks

Answer 1

The problem is in

header('Content-Length: ' . filesize($file) + 1);

Dot is evaluated before plus so your code is string + 1, result is 1 and this causes that 1 is sent as header. Correct code should be

header('Content-Length: ' . filesize($file));

because according to this page http://www.php.net/manual/en/function.readfile.php no +1 is used. Other solution is

header('Content-Length: ' . (filesize($file) + 1));

which will work as you want.