Download file from Slim Framework 2.4 - php

Question

I am trying to let the user download a file in the Slim php framework.
The intended use is that the file will be:
http://api.test.com/item/123.json <- returns json string with data
http://api.test.com/item/123.pdf <- download pdf-file with human-readable presentation of data
I have the code producing the PDF, but what I need is to make Slim send the correct headers so the file will be downloaded.
This is the following code I have (working) for the existing system:
header("Pragma: public");
header('Content-disposition: attachment; filename='.$f->name);
header('Content-type: ' .$f->type);
header('Content-Transfer-Encoding: binary');
echo $f->data;
Following is my current (non-working) Slim-code where the headers I declare is not sent to the browser. Instead I get text/html. (Note that this example only contains one header, I have also tested to see if any other header manipulation would cause any effect, but it haven't). The switch-case of json/pdf/xml will be added later on.
R::setup();
$app = new \Slim\Slim();
$app->get('/item', function() use ($app) {
$f = R::load('file', 123);
$app->response->headers->set("Content-Type", "application/pdf"); //$f->type
$app->response->setBody($f->data);
});
$app->run();
The $app->response->setBody($f->data) however works fine.

Answer 1

Problem solved. Turned out to be a included php class with whitespace in it. This messed up the headers i guess.
Solved by creating a new, empty project and include step by step until the bad class showed.
Working solution for setting headers inside a Slim function;
<?php
require 'vendor/autoload.php';
$app = new \Slim\Slim();
$app->get('/foo', function () use ($app) {
$app->response->headers->set('Content-Type', "application/pdf");
$app->response->setBody("foo");
});
$app->run();
?>
Updated: This is the headers I use to let a user download a PDF:
$app->response->headers->set('Content-Type', $f->type);
$app->response->headers->set('Pragma', "public");
$app->response->headers->set('Content-disposition:', 'attachment; filename=' . $f->name);
$app->response->headers->set('Content-Transfer-Encoding', 'binary');
$app->response->headers->set('Content-Length', $f->size);
$app->response->setBody($f->data);