For a lot of folks, the fact that there seemed to be no clear way to get PHP working with Apache 2 is THE reason they've stuck with the 1.2x or beter version of Apache. And, without PHP, no YABB SE. However, there really is no problem - getting PHP to work with Apache 2 is very easy.
I was all set to collate the details on how to do this, when I came across a website that does pretty much the same thing: for all the details of how to compile PHP 4 and Apache 2 (from source, under GNU/Linux), have a look at
http://www10.brinkster.com/ssruprai/comphp.aspThis page is very well done, and very accurate - highly recommended. If you follow the instructions on this site (but see below), you should have no problems in getting Apache and PHP working.
1) The only issue some folks might have is that its uses the 'module' approach to call PHP from within Apache. This isn't a big deal, but you'll run into some zeolots who don't like this approach. But then, they also trend to have issues with Apache 2 in general, on occasion.
2) there is a small error in the docs (the only one I've found) - it claims that the LoadModule command will be automatically added to the Apache configuration file (httpd.conf). No, it won't. You need to add it manually, but this is trivial.