[pka]

Let me rephrase. I am proposing that (barring very specific requirements which webdev doesn't justify) there's no such thing as a "good PHP developer". A good developer is a good developer, period.

A good developer will learn a new language in a reasonable amount of time and will be able to be productive and write good code in it.

A PHP-only (or X-only for that matter) developer is, by the definition above, not a good developer.

So why restrict oneself to some random pool of X-only people?

[brokentone]

In general, I agree. But getting to mastery level takes time even for really good developers. Certain jobs require master-level application of that language's constructs for efficiency, security, or other reasons.

[jschwartzi]

What would you call a good developer who knew PHP?

[pka]

A good developer :)