[php-src] Issue #7953: Calling ob_clean() after ob_start('gz_handler') unsets Content-Encoding

Issue: https://github.com/php/php-src/issues/7953 Comment Author: damianwadley ob_gzhandler isn't some special string that output buffering recognizes - it's an actual function - so it's not output buffering itself that is at fault. It's like you wrote your own callback that added a response header the first time it was called - that header will still be there after output buffering ends. I think it would be possible for ob_gzhandler to detect the PHP_OUTPUT_HANDLER_CLEAN flag and to unset the header and reset back to the initial state. (Equally possible in userland.) Or to remove the header automatically if there's been no output, but that would mean no more effectively-empty responses with just the compression container and instead actually-empty responses with no content at all, _but_ any good client should be totally okay with that.