function force_download($filename = '', $data = '', $set_mime = FALSE)
{
    if ($filename === '' OR $data === '')
    {
        return;
    }
    elseif ($data === NULL)
    {
        if ( ! @is_file($filename) OR ($filesize = @filesize($filename)) === FALSE)
        {
            return;
        }

        $filepath = $filename;
        $filename = explode('/', str_replace(DIRECTORY_SEPARATOR, '/', $filename));
        $filename = end($filename);
    }
    else
    {
        $filesize = strlen($data);
    }
    // Set the default MIME type to send
    $mime = 'application/octet-stream';

    $x = explode('.', $filename);
    $extension = end($x);

    if ($set_mime === TRUE)
    {
        if (count($x) === 1 OR $extension === '')
        {
            /* If we're going to detect the MIME type,
             * we'll need a file extension.
             */
            return;
        }

        // Load the mime types
        $mimes =& get_mimes();

        // Only change the default MIME if we can find one
        if (isset($mimes[$extension]))
        {
            $mime = is_array($mimes[$extension]) ? $mimes[$extension][0] : $mimes[$extension];
        }
    }

    /* It was reported that browsers on Android 2.1 (and possibly older as well)
     * need to have the filename extension upper-cased in order to be able to
     * download it.
     *
     * Reference: http://digiblog.de/2011/04/19/android-and-the-download-file-headers/
     */
    if (count($x) !== 1 && isset($_SERVER['HTTP_USER_AGENT']) && preg_match('/Android\s(1|2\.[01])/', $_SERVER['HTTP_USER_AGENT']))
    {
        $x[count($x) - 1] = strtoupper($extension);
        $filename = implode('.', $x);
    }

    if ($data === NULL && ($fp = @fopen($filepath, 'rb')) === FALSE)
    {
        return;
    }

    // Clean output buffer
    if (ob_get_level() !== 0 && @ob_end_clean() === FALSE)
    {
        @ob_clean();
    }

    // Generate the server headers
    header('Content-Type: '.$mime);
    header('Content-Disposition: attachment; filename="'.$filename.'"');
    header('Expires: 0');
    header('Content-Transfer-Encoding: binary');
    header('Content-Length: '.$filesize);
    header('Cache-Control: private, no-transform, no-store, must-revalidate');

    // If we have raw data - just dump it
    if ($data !== NULL)
    {
        exit($data);
    }

    // Flush 1MB chunks of data
    while ( ! feof($fp) && ($data = fread($fp, 1048576)) !== FALSE)
    {
        echo $data;
    }

    fclose($fp);
    exit;
}

$download_file_path = "{$_SERVER['DOCUMENT_ROOT']}/index.php";


force_download($download_file_path, null);