Adds Content-length Header For Downloads

[moebrowne]

When downloading files it is useful to send the content length header so that the browser can give the user some indication of progress, especially with large files

[ozdemirburak]

Great idea, but I think it is not correctly implemented as filename is a string. Something like this would be better, but I have not tested it.

public function convertAndDownload(?string $filename = null, bool $exit = true): void
{
    $filename = $filename ?? $this->filename;
    $convertedData = $this->convert();
    $this->sendHeaders($filename, $convertedData);
    echo $convertedData;
    if ($exit === true) {
        exit();
    }
}

protected function sendHeaders(string $filename, string $data): void
{
    header('Content-disposition: attachment; filename=' . $filename . '.' . $this->conversion['extension']);
    header('Content-type: ' . $this->conversion['type']);
    header('Content-length: ' . strlen($data));  // Use strlen() on the actual data
}