>> Need to find a PHP developer? No problem.
Not being able to hire just anyone to code for you is a good thing just as much as it is bad. It means you're going to have some pretty bright people working for you, which apparently is something Fog Creek values and can afford to do.
> Want a PHP IDE? No problem.
Most hackers have their own preferred editors anyways, and Emacs/vi/etc work well with any language if that's the editor you're experienced with.
>> A large community to handle bugs and any future development? Yes.
Again, that's a hindrance just as much as it is a benefit. If you need to make a change or fix a bug in the language, you're going to have much better luck if you know a bunch of people who are intimately familiar with how that language works, especially if their right down the hall from you.