Class 'MongoDB\Driver\Manager' not found

I do not know if it's the most elegant solution, but it worked for me:

1. Install the php driver $ sudo pecl install mongodb
2. Create the extension file $ sudo nano /etc/php5/mods-available/mongodb.ini and write inside: extension=mongodb.so
3. Create a symbolic link for this file $ sudo ln -sv /etc/php5/mods-available/mongodb.ini /etc/php5/apache2/conf.d/20-mongodb.ini
4. Create an other symbolic link for this file $ sudo ln -sv /etc/php5/mods-available/mongodb.ini /etc/php5/cli/conf.d/20-mongodb.ini
5. Restart apache or the server used $ sudo service apache2 restart

It may be necessary to reinstall jenssegers/mongodb: $ composer require jenssegers/mongodb

You may also need to restart fpm on ubuntu/debian

sudo service php7.0-fpm restart

for php5

sudo service php5-fpm restart

Also, make sure extension=mongodb.so is in:

apache2/php.inicli/php.inifpm/php.ini

to check i do:

locate php.ini | xargs grep mongo

to see php.ini files:

php --ini

As of 2017 this should work for PHP 5.6:

### Install MongoDB driver for PHP 5.6 ##############echo -e "\n### Installing MongoDB PHP driver ##\n";sudo apt-get install php-mongodb -y# Make sure extension=mongodb.so is presentPhpConfigFile="/etc/php/5.6/fpm/php.ini"if grep -q mongodb.so "$PhpConfigFile"; then  echo "extension=mongodb.so already found, dont add."else  echo "extension=mongodb.so" | sudo tee "$PhpConfigFile"  echo "Added extension=mongodb.so to $PhpConfigFile"fi

It is part of my one-liner installer of PHP5.6 + nginx + MongoDB plugin for PHP, I've even made a domain for it:http://ubuntu-script.tk