actually... i don't think that's what the problem is, jens. :-)
it looks like apache is trying to load the php binary from /usr/share/. i'm almost positive it's located in /usr/bin/.
a fix for this *might* be to create a symlink to the php binary located in the /usr/bin/ dir. try this:
ln -s /usr/bin/php /usr/share/php
that way when apache tried to load the php binary from /usr/share/ it will be redirected to /usr/bin/.
i could be way off though, but with any luck this was a quick fix. :-)