HHVM compatibility update

[elazar]

From the FAQ:

The SDK does not currently run on HHVM, and won't be able to until the issue with the yield syntax in HHVM is resolved.

The last comment on that issue indicates that it was resolved in the HHVM 3.11 release for all cited use cases, which should include the AWS SDK as it was mentioned a few times. I'm not seeing any open HHVM issues directly related to support for the yield keyword, at least.

The current failure on the HHVM build of aws/aws-sdk-php doesn't appear to be related to the original issue with yield. It would be great if we could get an SDK version with full HHVM compatibility.

[jeskew]

Unfortunately, Travis only tests against HHVM 3.6.6 at the moment. The latest failure of the current version of the SDK (V3) was caused by the yield syntax incompatibility. Based on what was mentioned in the HHVM issue, I expect v3 would work on HHVM 3.11, but I don't have a good way to automatically test all releases and pull requests until Travis upgrades their HHVM runtime.

The V2 failure linked to appears to be caused by an HHVM incompatibility in PHPUnit. I haven't investigated what's causing it, but it might also be fixed in 3.11.

[elazar]

@jeskew Don't know that this is an option you can consider, but it looks like it's possible to use HHVM 3.11 in a Trusty beta environment. See this issue for details.

[jeskew]

I ran a test (#902) to see if the SDK was compatible with HHVM >=3.11. It appears that while the HHVM team fixed the syntax error that was thrown when yield was placed inside parentheses, yielding into generators still does not work the same in PHP and HHVM.

[jeskew]

I opened a new issue on HHVM, as there is still an incompatibility with the way generators work between HHVM 3.11 and Zend PHP.