Add an apk package for php-mongo
Please add php mongo extension package. Manual installation is a pain and by the time you get everything working you end up with half a gig of rubbish.
http://php.net/manual/en/mongo.installation.php
https://github.com/mongodb/mongo-php-driver
(from redmine: issue id 4278, created on 2015-06-08, closed on 2018-08-22)