I am working on a project and I need to use Google Analytics server side. I do not need to retrieve information, but I need to send information. I could
You send data via the Measurement Protocol. No special library or dev kit is required, you simply append parameters to the GA endpoint and send them via Curl/fopen/sockets/whatever to Google Analytics.
Each calls includes at least the ID of the account you want to send data to, a client id that allows to group interactions into sessions (so it should be unique per visitor, but it must not identify a user personally), an interaction type (pageview, event, timing etc., some interactions types require additional parameters) and the version of the protocol you are using (at the moment there is only one version).
So the most basic example to record a pageview would look like this:
www.google-analytics.com/collect/v=1&tid=UA-XXXXY&cid=555&t=pageview&dp=%2Fmypage