Detecting if user can accept gzip?

[Mark Hewitt]

I'm thinking of including a hack in my forum which would provide extra information in forumdisplay, (specifically a preview of each thread).

However being mindful of bandwidth usage etc, I would like to be able to send the "enhanced" version of the page only to those who have opted to receive it and are able to get gzipped versions of the pages, it would likely use too many resources to send it un-gzipped.

So is there a way I can do e.g.
if($bbuser == gzipOn)
{
// do this
}

Thanks

Mark.