Response

Your Slim app’s routes and middleware are given a PSR 7 response object that represents the current HTTP response to be returned to the client. The response object implements the PSR 7 ResponseInterface with which you can inspect and manipulate the HTTP response status, headers, and body.

How to get the Response object

The PSR 7 response object is injected into your Slim application routes as the second argument to the route callback like this:

<?php
use Psr\Http\Message\ServerRequestInterface;
use Psr\Http\Message\ResponseInterface;

$app = new \Slim\App;
$app->get('/foo', function (ServerRequestInterface $request, ResponseInterface $response) {
    // Use the PSR 7 $response object

    return $response;
});
$app->run();

The PSR 7 response object is injected into your Slim application middleware as the second argument of the middleware callable like this:

<?php
use Psr\Http\Message\ServerRequestInterface;
use Psr\Http\Message\ResponseInterface;

$app = new \Slim\App;
$app->add(function (ServerRequestInterface $request, ResponseInterface $response, callable $next) {
    // Use the PSR 7 $response object

    return $next($request, $response);
});
// Define app routes...
$app->run();

The Response Status

Every HTTP response has a numeric status code. The status code identifies the type of HTTP response to be returned to the client. The PSR 7 Response object’s default status code is 200 (OK). You can get the PSR 7 Response object’s status code with the getStatusCode() method like this.

$status = $response->getStatusCode();

You can copy a PSR 7 Response object and assign a new status code like this:

$newResponse = $response->withStatus(302);

The Response Headers

Every HTTP response has headers. These are metadata that describe the HTTP response but are not visible in the response’s body. Slim’s PSR 7 Response object provides several methods to inspect and manipulate its headers.

Get All Headers

You can fetch all HTTP response headers as an associative array with the PSR 7 Response object’s getHeaders() method. The resultant associative array’s keys are the header names and its values are themselves a numeric array of string values for their respective header name.

$headers = $response->getHeaders();
foreach ($headers as $name => $values) {
    echo $name . ": " . implode(", ", $values);
}

Get One Header

You can get a single header’s value(s) with the PSR 7 Response object’s getHeader($name) method. This returns an array of values for the given header name. Remember, a single HTTP header may have more than one value!

$headerValueArray = $response->getHeader('Vary');

You may also fetch a comma-separated string with all values for a given header with the PSR 7 Response object’s getHeaderLine($name) method. Unlike the getHeader($name) method, this method returns a comma-separated string.

$headerValueString = $response->getHeaderLine('Vary');

Detect Header

You can test for the presence of a header with the PSR 7 Response object’s hasHeader($name) method.

if ($response->hasHeader('Vary')) {
    // Do something
}

Set Header

You can set a header value with the PSR 7 Response object’s withHeader($name, $value) method.

$newResponse = $oldResponse->withHeader('Content-type', 'application/json');

Append Header

You can append a header value with the PSR 7 Response object’s withAddedHeader($name, $value) method.

$newResponse = $oldResponse->withAddedHeader('Allow', 'PUT');

Remove Header

You can remove a header with the Response object’s withoutHeader($name) method.

$newResponse = $oldResponse->withoutHeader('Allow');

The Response Body

An HTTP response typically has a body. Slim provides a PSR 7 Response object with which you can inspect and manipulate the eventual HTTP response’s body.

Just like the PSR 7 Request object, the PSR 7 Response object implements the body as an instance of \Psr\Http\Message\StreamInterface. You can get the HTTP response body StreamInterface instance with the PSR 7 Response object’s getBody() method. The getBody() method is preferable if the outgoing HTTP response length is unknown or too large for available memory.

$body = $response->getBody();

The resultant \Psr\Http\Message\StreamInterface instance provides the following methods to read from, iterate, and write to its underlying PHP resource.

• getSize()
• tell()
• eof()
• isSeekable()
• seek()
• rewind()
• isWritable()
• write($string)
• isReadable()
• read($length)
• getContents()
• getMetadata($key = null)

Most often, you’ll need to write to the PSR 7 Response object. You can write content to the StreamInterface instance with its write() method like this:

$body = $response->getBody();
$body->write('Hello');

You can also replace the PSR 7 Response object’s body with an entirely new StreamInterface instance. This is particularly useful when you want to pipe content from a remote destination (e.g. the filesystem or a remote API) into the HTTP response. You can replace the PSR 7 Response object’s body with its withBody(StreamInterface $body) method. Its argument MUST be an instance of \Psr\Http\Message\StreamInterface.

$newStream = new \GuzzleHttp\Psr7\LazyOpenStream('/path/to/file', 'r');
$newResponse = $oldResponse->withBody($newStream);

Returning JSON

Slim’s Response object has a custom method withJson($data, $status, $encodingOptions) to help simplify the process of returning JSON data.

The $data parameter contains the data structure you wish returned as JSON. $status is optional, and can be used to return a custom HTTP code. $encodingOptions is optional, and are the same encoding options used for json_encode().

In it’s simplest form, JSON data can be returned with a default 200 HTTP status code.

$data = array('name' => 'Bob', 'age' => 40);
$newResponse = $oldResponse->withJson($data);

We can also return JSON data with a custom HTTP status code.

$data = array('name' => 'Rob', 'age' => 40);
$newResponse = $oldResponse->withJson($data, 201);

The Content-Type of the Response is automatically set to application/json;charset=utf-8.

If there is a problem encoding the data to JSON, a \RuntimeException($message, $code) is thrown containing the values of json_last_error_msg() as the $message and json_last_error() as the $code.