The simplest way to install driver for php is using pecl.
When I tried to run:
pecl install mongo
It failed with error:
pecl/mongo requires PHP (version >= 5.3.0, version <= 5.99.99), installed version is 7.0.27 No valid packages found install failed
So, if you have higher version of php, like in my case: 7.0.27
You have to run command:
pecl install mongodb