Installation
PHP Manual

HHVM

HHVM users should download the latest from » S3 for the time being.

Once downloaded, execute the following steps:

hphpize
cmake .

make configlib

make -j 5
make install

Add the following line to your php.ini file (usually found in /etc/hhvm):

hhvm.dynamic_extension_path=/usr/local/hhvm/3.9.1/lib/hhvm/extensions/20150212
hhvm.dynamic_extensions[mongodb]=mongodb.so


Installation
PHP Manual