Best way to transfer legacy PHP code to a modern framework?

rzack writes: Since 1999, I've written a huge amount of PHP code, for dozens of applications and websites. Most of it has been continually updated, and remains active and in-production, in one form or another. Here's the thing, it's all hand-written using vi, even to this day. Is there any benefit to migrating this codebase to a more modern PHP framework, like Laravel? And is there an easy and minimally intrusive way this can be done en-masse, across dozens of applications and websites? Or at this point should I just stick with vi?