Slim - 如何发送带有“Content-Type：application/json”标头的响应？

我有这个简单的 REST api，用 Slim 完成，

<?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();

但是，我无法让浏览器向我发送application/json内容类型，它 总是发送text/html？我做错了什么？

EDIT:

好吧，经过两个小时的头撞墙后，我偶然发现了这个答案：

https://github.com/slimphp/Slim/issues/1535 https://github.com/slimphp/Slim/issues/1535（在页面底部） 这解释了发生了什么，似乎response对象是不可变的并且 因此，如果您想在之后归还它，则必须归还或重新分配它 尽管。

所以，而不是这个：

if($student) {
            $response->withHeader('Content-Type', 'application/json');
            $response->write(json_encode($student));
            return $response;

        } else { throw new PDOException('No records found');}

这样做：

if($student) {
    return $response->withStatus(200)
        ->withHeader('Content-Type', 'application/json')
        ->write(json_encode($student));

} else { throw new PDOException('No records found');}

一切都很好。