Here you go -- a classic post by Hacker News heartthrob Derek Sivers, founder of CD Baby,
"7 Reasons I Switched Back to PHP":
http://sivers.org/rails2php
I threw away 2 years of Rails code, and opened a new empty Subversion respository.
Then in a mere TWO MONTHS, by myself, not even telling anyone I was doing this, using nothing but vi, and no frameworks, I rewrote CD Baby from scratch in PHP. Done! Launched! And it works amazingly well.
Mind you, this is from 2007 and there's more to the story -- Sivers learned a lot, as he says, from hiring a Rails guy and from the attempt to use Rails:
It’s the most beautiful PHP I’ve ever written, all wonderfully MVC and DRY, and and I owe it all to Rails.
At the end, he describes his 7 reasons why PHP worked out better in his case and they may well make sense in other cases as well -- that is, while some of these reasons reflect his personal tastes (e.g. #6 - I LOVE SQL), some are solid business reasons, like reason #2, which I'll quote in its entirety, since it's worth keeping such considerations in mind:
#2 - OUR ENTIRE COMPANY’S STUFF WAS IN PHP: DON’T UNDERESTIMATE INTEGRATION
By the old plan (ditching all PHP and doing it all in Rails), there was going to be this One Big Day, where our entire Intranet, Storefront, Members’ Login Area, and dozens of cron shell scripts were ALL going to have to change. 85 employees re-trained. All customers and clients calling up furious that One Big Day, with questions about the new system.
Instead, I was able to slowly gut the ugly PHP and replace it with beautiful PHP. Launch in stages. No big re-training.
I'll suggest that, like other writings by Sivers, this is worth reading since the issues he dealt with in migrating to a rewritten system are ones that are not uncommon.
(For a list of all his blog posts about entrepreneurship, music (and the business of music), life, etc.:
http://sivers.org/blog )