Whilst we still have a dependency on pear in the travis.yml script hhvm won't work. Hopefully with composer in 3.4 we can get things running with an allowed failure here. I'll close it for now. But if you want to work on refactoring travis to avoid using pear then feel free to submit another PR to do so. I'll definitely be interested in that!
nicksavov
- 
brianteeman
- 
related article for this pull: http://www.hhvm.com/blog/2813/we-are-the-98-5-and-the-16