You convince people that they will have a career with your company and then hire for that. There are people who are looking for a good career over "bleeding edge" -- some of them are even good. (I've worked with some, although even in such institutions, those who are good are in the minority -- and often incorporating newer technologies into side or non-critical projects where they make sense and save time/effort/money/bureaucracy.)

If you can't convince such talent that you can offer a career, then you may be screwed.

P.S. Is PHP significantly coincident with such "career" type positions, these days?