Install MongoDbBundle with Symfony2

are you sure you have the mongo extension ?

run this from console

 php -i | grep mongo

are there the mongo configs ?

if so add

phpinfo();

to your app/app_dev.phpand check if Symfony(apache) is using another php than your shell PATH

UPDTE:

as pointed out in comments, your apache uses another php than you expectpoint the apache to the correct php extension path in httpd.conf

php mongodb symfony composer-php

this is the solution for osx:

brew install php56-mongo

if it errors out then read the package name and re-run such as - example:

example: brew install php5789-mongo

CodeHunter