PHP: force an image download from above directory root?

I'm attempting to force a download of an image that is in a directory above my website 开发者_高级运维root. The download happens ok, and the correct filename is saved. However, the end-file is not a valid image and will not open or display properly. Here's my code:

        $photograph = new ViewPhotograph($photograph_id);
        $photograph->setPhotographVars();

        $file = $photograph->getPath('small');
        $filename = '1.jpg';

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

do a ob_start before calling ob_clean()

once something is outputed by using echo or similar, you can't get rid of this, except, when you start a buffer before

Perhaps there's a PHP warning corrupting the stream.

Comment out the headers and see if you see a warning. If you do, fix it. (note that you shouldn't have display_errors turned on production servers).