GuzzleHttp\Psr7\MultipartStream::createElement PHP Method

    private function createElement($name, StreamInterface $stream, $filename, array $headers)
    {
        // Set a default content-disposition header if one was no provided
        $disposition = $this->getHeader($headers, 'content-disposition');
        if (!$disposition) {
            $headers['Content-Disposition'] = $filename === '0' || $filename ? sprintf('form-data; name="%s"; filename="%s"', $name, basename($filename)) : "form-data; name=\"{$name}\"";
        }
        // Set a default content-length header if one was no provided
        $length = $this->getHeader($headers, 'content-length');
        if (!$length) {
            if ($length = $stream->getSize()) {
                $headers['Content-Length'] = (string) $length;
            }
        }
        // Set a default Content-Type if one was not supplied
        $type = $this->getHeader($headers, 'content-type');
        if (!$type && ($filename === '0' || $filename)) {
            if ($type = mimetype_from_filename($filename)) {
                $headers['Content-Type'] = $type;
            }
        }
        return [$stream, $headers];
    }