Owen Yamauchi
d7c2eac643
This is gone as of Zend 5.4: as far as I can tell, anything other than a positive integer literal is a parse error (including constants, "1 + 1", etc.) Let's get rid of it. The mere fact that this construct ever existed in any programming language is deeply horrifying. This lets us get rid of all the goofy code that subtracts 1 from the top value on the stack, does IterFree if needed, and jumps to the next level. Now, we can hardcode the necessary IterFrees and do a single jump, right where the break/continue actually is. The error message for using a non-integer expression is less helpful than Zend's (Zend says "non-constant operand not supported"; ours is "unexpected T_VARIABLE" or whatever). It wouldn't be that hard to do in our parser, if we think that's helpful. I don't think it matters, though.
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.