Architecture / Installation

Ok, I've tried checking other forums posts, the docs, faqs, and even Google and I'm still stumped on this one. I've tried to upgrade my 2.4 to 3.1, both with Fantastico and by myself, and both give me the same result: a page that says "PHP5 is required for Tiki 3.0" So I've double checked with my host, and they are running 5.2.5. They do have an option to use other versions by modifying the .htaccess file, but those versions are 5.1 and 5.0, so they are all 5. Regardless, since it wasn't working anyway, I tried modifiying the .htaccess file (a couple different ways too, since I had slightly different instructions on how to do it), but no dice. I don't know what else to do here. My host btw is Siteground which I understand is normally very Tiki-friendly so I'm really confused why this is happening. 😕