Python vs. PHP

[ll]

I already have a pretty large existing code base on an interactive
website written in PHP.  I'm very happy with the performance and ease of
use, integration with MySQL and Apache.  (The  "trinity" of web
development).

I've been playing around with python recently and have written a few CGI
scripts with it, but I am reluctant to devote too much effort into
Python development.

How does Python stack up against PHP in terms of performance?  PHP runs
as a module in Apache, I think, whereas Python runs in a seperate
process.  What kind of overhead is there in starting up the VM for each
page hit?  How well does it scale?

I have heard of Zope, but don't know a great deal about it.  It seems
more like an entire framework for a website--how well would it integrate
with my existing codebase?

Drop in any other ideas/thoughts you have about the comparison

Luke