My two cents. Hopefully this won't turn into a flame war.
OOP, strict php 5, mvc, with a some nice ORM inspired by active record. If you are looking for super easy docs to get you started, checkout the http://codeigniter.com to get you started (kohana is/was forked from CI)
p.s. kohana 3 is the newest version which you can get from github, it's a lot different from 2.x and contains a database mapper called "sprig" i believe. It's supposed to be django-esque but I'm not familiar with django to say anything about that ... only check it out!
Also if you want to go the ruby route, of course there's ROR but do take a second to look into sinatra, it's SUPER easy. it's simplicity is thus - beautiful.
However, I think Python is a better investment all around.
Ruby and Python are better suited for growing beyond the web and into great areas.
In my entourage I believe Ruby is more of a startup language and Python more of an entreprise language. Though both see their fair share of use in both.
I started learning PHP in 2001, coming from web development in ASP3 written in VBScript. At the time, developing pages in PHP and VBScript was very similar, and it was really more a matter of learning the few syntax differences and the core library.
Python is a much different language than PHP and VBScript, and as a result working on learning it has made me a much better programmer and it has been a lot more interesting because I'm working with concepts that I might not otherwise cross paths with in my day-to-day programming and gives me a leg up as these concepts are added to php.
If you haven't already, please also consider learning javascript. There's a lot of nascent node.js webframeworks that you could start with.
You can always do Ruby/Python afterwards. It's easy to go from one to the other.
You might want to do an app with Rails and Django (or some other framework -- many to chose from) and see how you like it.
Try them all. Do a 'hello world' project in each. Use the one you love. They're all fine, and many people have written many successful sites with all three.