You have drupal 7 image from docker hub, and want to connect tomongo db via php code.

The Dockerfile for this is:

FROM drupal:7.57-apache

RUN apt-get update; \
	apt-get install openssl libssl-dev libcurl4-openssl-dev -y; \
	pecl install mongodb; \
	echo "extension=mongodb.so" > /usr/local/etc/php/conf.d/mongodb.ini \

Build the image

docker build -t drupal-with-mongo .

Run Container

docker run --name drupal-with-mongo -p 8080:80 -d drupal-with-mongo

Download Dockerfile

You can get the file from github at:https://github.com/GyanBlog/drupal7-with-mongo

You can mount volume, if you want.

Enjoy!