system/HTTP/DownloadResponse.php
private function getContentDisposition() : string
	{
		$download_filename = $this->getDownloadFileName();

		$utf8_filename = $download_filename;

		if (strtoupper($this->charset) !== 'UTF-8')
		{
			$utf8_filename = mb_convert_encoding($download_filename, 'UTF-8', $this->charset);
		}

		$result = sprintf('attachment; filename="%s"', $download_filename);

		if (isset($utf8_filename))
		{
			$result .= '; filename*=UTF-8\'\'' . rawurlencode($utf8_filename);
		}

		return $result;
	}
private function getContentDisposition() : string
	{
		$download_filename = $this->getDownloadFileName();

		$utf8_filename = $download_filename;

		if (strtoupper($this->charset) !== 'UTF-8')
		{
			$utf8_filename = mb_convert_encoding($download_filename, 'UTF-8', $this->charset);
		}

		$result = sprintf('attachment; filename="%s"', $download_filename);

		if (isset($utf8_filename))
		{
			$result .= '; filename*=UTF-8\'\'' . rawurlencode($utf8_filename);
		}

		return $result;
	}
get Content-Disposition Header string.

@return string