Thanks guys for the quick responses.
I finally got it working by installing the great PHP package by Marc Liyanage.
http://www.entropy.ch/software/macosx/php/#install
PHP still seems broken in 7B85, just like in the previous betas I've tried. With Apache turned on, PHP scripts do not compile and show up as text in Safari. Anyone got PHP to work??
Installed Marc Liyanage's PHP module and followed the on-screen instructions correctly, but now personal web sharing just gets stuck and refuses to start...