- Input Processing and sanitize (GET/POST/COOKIE)
- Session Management
- Database Access without surprises
- Syntactic sugar for callbacks
- Template processing
- XML, HTML, JSON processing
These are stuff that PHP should already have in some kind of fast internal c code, but it simply fails to deliver. Frameworks fill the gap. If HHVM provides substantial better alternatives and people use HHVM then Frameworks will use these extensions.
Framework code is already filled with edge case handling for different PHP Versions, adding a case for HHVM isn’t a problem.