Fabien Potencier has a new post to his site showing how you can package a Symfony application into one file, the first part of a series. It's not "packing" like you'd think with a phar, but more of an all-in-one file setup.
Sometimes, I'm wondering if I'm not just completely crazy. [...] his is yet another step toward my Quest of the PHP Holy Grail. But besides being a though challenge, there are many other reasons that makes it interesting for everyone. First, that's a good way to learn more about the Symfony internals and especially about the Kernel class. [...] Then, I want to showcase once more the flexibility of the Symfony core framework and the decoupling between all aspects of the framework.
He does talk about one more practical use - making bug reporting easier by having just one file that can reproduce the behavior you're seeing and is easy to drop in, self-contained. He issues a challenge to himself for the course of the series - is it possible to make a full-stack application in one file and in under 200 lines of code.