Hi!
I can say that PHP 7 locally runs unit tests
significantly faster than PHP
5.6, although that's not really a representative workload for running a
website.
PHP 7 is faster than 5.6, and probably be on almost any workload, from
my experience (the degree of speedup would vary of course). As for
comparison with hhvm, I heard various reports, but I think spending some
time on seriously testing it (I mean creating proper production setup,
and directing either captured/replayed or real traffic to it) is the
best way to go.
--
Stas Malyshev
smalyshev(a)wikimedia.org