Note that this was posted in late Oct 2013, whereas according to the HHVM blog[1] there were major stability, unit test, and performance improvements made to HHVM for a variety of frameworks (including Symfony) in mid December, thus this may be slightly out of date.

[1] http://www.hhvm.com/blog/2813/we-are-the-98-5-and-the-16

indeed .. the numbers should be even better now.

I'd suggest submitting to http://www.techempower.com/benchmarks/

I'm surprised at the huge gain from going to php 5.3 with Apc to 5.5 with send opcache...