In general, a test which gets its input piped in is not really interacting with a terminal like it normally would. Thus, letting it think it has the same terminal as the environment is incorrect. More specifically, hphpd uses Readline, which inspects the TERM env var and based on that and a stunning array of other options will attempt to initialize the terminal with extra control characters on first use. It would be tough to try to control for all of the different options and ensure they're all the same, and honestly testing Readline is not the objective of our tests anyway. Thus, I'm forcing TERM to 'dumb' when a test has input to ensure a) a simple terminal which requires no control characters and b) consistency no matter what environment is present when the tests are run.
HipHop VM for PHP 
HipHop VM (HHVM) is a new open-source virtual machine designed for executing programs written in PHP. HHVM uses a just-in-time compilation approach to achieve superior performance while maintaining the flexibility that PHP developers are accustomed to. HipHop VM (and before it HPHPc) has realized > 5x increase in throughput for Facebook compared with Zend PHP 5.2.
HipHop is most commonly run as a standalone server, replacing both Apache and modphp.
Installing
You can install a prebuilt package or compile from source.
Running
You can run standalone programs just by passing them to hhvm: hhvm my_script.php.
HipHop bundles in a webserver. So if you want to run on port 80 in the current directory:
sudo hhvm -m server
For anything more complicated, you'll want to make a config.hdf and run sudo hhvm -m server -c config.hdf.
Contributing
We'd love to have your help in making HipHop better. If you run into problems, please open an issue, or better yet, fork us and send a pull request. Join us on #hhvm on freenode.
If you want to help but don't know where to start, try fixing some of the Zend tests that don't pass. You can run them with hphp/test/run. When they work, move them to zend/good and send a pull request.
Before changes can be accepted a Contributors Licensing Agreement (pdf - print, sign, scan, link) must be signed.
Licence
HipHop VM is licensed under the PHP and Zend licenses except as otherwise noted.