Hello I want to create a simple blog where users can post comments, but I don't really want to get into one of the heavier code generators or frameworks like Django or RoR or Wordpress. Reason is I need to learn this stuff from the inside out, given that my project will require a lot of programming "from basics" in the future (since it'll evolve into a specialist finance-oriented site with user-submittable portfolios, which is actually quite a big evolution from a blog, even if the initial structure is similar). I'm an accomplished finance/quant programmer but am fairly new to web development. 

What's the best, "lean and mean" piece of source code that might get me started? Something I can easily customize to my own vision?. KISS-principle applies, but I'd like it to do basics like users and authentification and stuff ideally though. 

Would prefer pure PHP and/or Python, but am open to suggestions.