Basic usage:

hhvm -m server -p 8080
hhvm whatever.php
# binaries
# hack to php
/usr/bin/h2tp
/usr/bin/hack_remove_soft_types
/usr/bin/hackificator
/usr/bin/hh_client
/usr/bin/hh_format
/usr/bin/hh_server
/usr/bin/hhvm
 
# php containers code
/usr/share/hhvm/hack/hacklib/containers
 
# relevant config files
/etc/apache2/mods-available/hhvm_proxy_fcgi.conf
/etc/default/hhvm
/etc/hhvm/php.ini
/etc/hhvm/server.ini
/etc/init.d/hhvm
 
# logger
/var/log/hhvm/error.log

transpiling

h2tp <src> <dst> --no-collections

install

controllare la procedura dal sito docs

wget -O - http://dl.hhvm.com/conf/hhvm.gpg.key | sudo apt-key add -
echo deb http://dl.hhvm.com/ubuntu trusty main | sudo tee /etc/apt/sources.list.d/hhvm.list
sudo apt-get update
sudo apt-get install hhvm

una volta installato il pacchetto distro aggiornato verificare i files installati per intergrarsi in apache

# vi /etc/apache2/mods-available/hhvm_proxy_fcgi.conf
 
# ProxyPassMatch ^/(.+\.(hh|php)(/.*)?)$ fcgi://127.0.0.1:9000/var/www/$1
ProxyPassMatch ^/(.+\.(hh)(/.*)?)$ fcgi://127.0.0.1:9000/var/www/$1
 
Setting up hhvm (3.17.1~xenial) ...
********************************************************************
* HHVM is installed.
*
* Running PHP web scripts with HHVM is done by having your
* webserver talk to HHVM over FastCGI. Install nginx or Apache,
* and then:
* $ sudo /usr/share/hhvm/install_fastcgi.sh
* $ sudo /etc/init.d/hhvm restart
* (if using nginx)  $ sudo /etc/init.d/nginx restart
* (if using apache) $ sudo /etc/init.d/apache restart
*
* Detailed FastCGI directions are online at:
* https://github.com/facebook/hhvm/wiki/FastCGI
*
* If you're using HHVM to run web scripts, you probably want it
* to start at boot:
* $ sudo update-rc.d hhvm defaults
*
* Running command-line scripts with HHVM requires no special setup:
* $ hhvm whatever.php
*
* You can use HHVM for /usr/bin/php even if you have php-cli
* installed:
* $ sudo /usr/bin/update-alternatives \
*    --install /usr/bin/php php /usr/bin/hhvm 60
********************************************************************

Async

it's not exactly multitasking, it still allows you to run separate blocks of code in parallel: while one is waiting on something that is not blocked on CPU (e.g. for an API response to come back), the other be executed already.

<?hh
async function api(): Awaitable<string> {
    //
    // Let's pretend we've just executed an API call
    // and are now waiting for it to come back with
    // a response. While that's being done, CPU should
    // be free to execute code elsewhere.
    //
    await SleepWaitHandle::create(1000); // 1ms

    return 'api result';
}

async function cpu(): Awaitable<string> {
    //
    // Let's pretend we're doing some CPU-heavy stuff.
    //
    usleep(500); // 0.5ms

    return 'cpu result';
}

$time = microtime(true);

//
// Execute both code blocks - while api() is waiting
// for the response, CPU-bound code will already be
// executed (thus losing less time idling until we
// hear back from the API call.)
// After that, wait until both async blocks are done
// and get their results.
//
$asyncApi = api();
$asyncCpu = cpu();
$resultApi = $asyncApi->getWaitHandle()->join();
$resultCpu = $asyncCpu->getWaitHandle()->join();

//
// Time elapsed will only be slightly over 1ms,
// instead of the expected 1ms (API) + 0.5ms (CPU)
// because we were able to execute the CPU-intensive
// code while we were waiting on the API response.
//
echo microtime(true) - $time;