Ajax post not working, can't figure this one out

EDIT:
And just like that i've found the problem, the header send in the Ajax request 'Content-Type: application/json' caused my issue. The minute i removed that from the headers array i'm receiving the post with $request->getPost();.

Congratulations. But why did you put the header then?

Something I already forgot how this your jQuery works. 

 $_POST An associative array of variables passed to the current script via the HTTP POST method when using application/x-www-form-urlencoded or multipart/form-data as the HTTP Content-Type in the request.