Slim v3 PUT method and retrieve POST data

I have added route to update emails in a database which uses PUT method

$app->put('/notifications/{email}', 'add_email_address');

and function for it looks like:

function add_email_address($request, $response, $args)  {

  $email = $args['email'];
      $addon_email = $request->getParam('addon_email', null);

      echo "ADD/UPDATE $email with $addon_email";


somehow on testing PUT method with a form input post addon_email = retrieved value for $addon_email is empty

Any tips what I’m doing wrong?

I have got it to work by changing

$addon_email = $app->request->getParam('addon_email', null);


$allPostPutVars = $request->getParsedBody();
$addon_email = $allPostPutVars['addon_email'];

It looks like getParam works only for GET method. Also content-type must be set as x-www-form-urlencoded