Handling large file download

It clearly not the problem with php code because same code works on dev server and it is processing files which are even larger than my whole docker VM memory.

And as far as I can see, laravel's Storage::download already using streamed responses behind the end:

    /**
     * Create a streamed response for a given file.
     *
     * @param  string  $path
     * @param  string|null  $name
     * @param  array|null  $headers
     * @param  string|null  $disposition
     * @return \Symfony\Component\HttpFoundation\StreamedResponse
     */
    public function response($path, $name = null, array $headers = [], $disposition = 'inline')
    {
        $response = new StreamedResponse;

        $filename = $name ?? basename($path);

        $disposition = $response->headers->makeDisposition(
            $disposition, $filename, $this->fallbackName($filename)
        );

        $response->headers->replace($headers + [
            'Content-Type' => $this->mimeType($path),
            'Content-Length' => $this->size($path),
            'Content-Disposition' => $disposition,
        ]);

        $response->setCallback(function () use ($path) {
            $stream = $this->readStream($path);

            while (! feof($stream)) {
                echo fread($stream, 2048);
            }

            fclose($stream);
        });

        return $response;
    }

I managed to solve the problem by setting

output_buffering = 0

in php.ini on production server. But I still don't get why it works on dev server. phpinfo() shows that output_buffering had same setting on both servers before which was 4096.