i just managed to install dokuwiki on an embedded system running openwrt. It's basically functional, but the screen layout is all wrong. Parts of the page are sort of 'piled' on atop the other. For example, Page Tools (Show pagesource, old revisions, backlinks, Back to top) are not buttons on the side, but rather written out in full at the bottom. I've had to install php extensions like json, xml, etc.
The datadir ('pages') at ./data/pages is not found, isn't accessible or writable. You should check your config and permission settings. Or maybe you want to run the installer?