Slim - How to send response with "Content-Type: application/json" header?

Question

I have this simple REST api, done in Slim,

<?php  require '../vendor/autoload.php';  function getDB() {     $dsn = 'sqlite:/home/branchito/personal-projects/slim3-REST/database.sqlite3';      $options = array(         PDO::ATTR_PERSISTENT => true,         PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION     );     try {          $dbh = new PDO($dsn);          foreach ($options as $k => $v)             $dbh->setAttribute($k, $v);          return $dbh;     }     catch (PDOException $e) {         $error = $e->getMessage();     } }  $app = new \Slim\App();  $app->get('/', function($request, $response) {     $response->write('Bienvenidos a Slim 3 API');     return $response; });  $app->get('/getScore/{id:\d+}', function($request, $response, $args) {      try {         $db = getDB();         $stmt = $db->prepare("SELECT * FROM students             WHERE student_id = :id             ");          $stmt->bindParam(':id', $args['id'], PDO::PARAM_INT);         $stmt->execute();          $student = $stmt->fetch(PDO::FETCH_OBJ);          if($student) {             $response->withHeader('Content-Type', 'application/json');             $response->write(json_encode($student));          } else { throw new PDOException('No records found');}      } catch (PDOException $e) {          $response->withStatus(404);         $err =  '{"error": {"text": "'.$e->getMessage().'"}}';         $response->write($err);     }     return $response; });  $app->run(); 

however, I can't get browser to send me application/json content type, it always sends text/html? What I am doing wrong?

EDIT:

Ok, after two hours of hitting the head against the wall, I stumbled upon this answer:

https://github.com/slimphp/Slim/issues/1535 (at the bottom of a page) which explains what happens, appears that response object is immutable and as such it must be returned or reassigned if you want to return it after while.

Answer 1

So, instead of this:

if($student) {             $response->withHeader('Content-Type', 'application/json');             $response->write(json_encode($student));             return $response;          } else { throw new PDOException('No records found');} 

Do like this:

if($student) {     return $response->withStatus(200)         ->withHeader('Content-Type', 'application/json')         ->write(json_encode($student));  } else { throw new PDOException('No records found');} 

And all is well and good.

Answer 2

For V3, withJson() is available.

So you can do something like:

return $response->withStatus(200)                 ->withJson(array($request->getAttribute("route")                 ->getArgument("someParameter"))); 

Note: Make sure you return the $response because if you forget, the response will still come out but it will not be application/json.