I assume you know that they originally recorded the play's ending for the movie? Test audiences *hated* it, so they went back, re-recorded and changed it to the happier ending.
Unfortunatly, the alternate ending isn't included on the DVD. Originally, they released a special edition that included a very rough cut of the alternate ending, but, apparently, there was some issues with who owned the rights and they recalled the DVD (making it the first major DVD release to be recalled due to content, thus making it a collector's item that catches $100+ on eBay) and re-released the version without the alternate ending.
You can find the alternate ending on the internet though.