> Regarding the progress indicator: it looks to me like it will be very > difficult to implement properly in PHP, but I might be completely > misunderstanding the design. If you think a PoC is possible, could you > please prepare one and maybe then we can come back to this discussion.
Example of such feature already present in PHP [1]. Callback function should post progress data into external storage (redis, session). That data may be then exposed to user via separate endpoint call. IMHO this is super useful feature. [1]: https://www.php.net/manual/session.upload-progress.php
