If php / pdo can lumen can. Lumen is a php framework.
http://stackoverflow.com/questions/18354638/json-post-and-decode-array-to-php

If the json is not formatted correctly it will just silently fail to parse it

Thanks for the replies! I got it working now.

The answer I was looking for was to use the Request::json()->get method, to extract the JSON data from the request.

So, posting a request like this...

POST / HTTP/1.1
Host: localhost
Content-Type: application/json

{
    "name": "dave"
}

...and accessing the data using something like...

$app->post('/', function() use ($app) {
    dd(Request::json()->get('name'));
});

Maybe useful for someone else. Thanks!

I wrote about this topic - "How to Submit a JSON POST Request in Lumen" - https://medium.com/@paulredmond/how-to-submit-json-post-requests-to-lumen-666257fe8280