# Response [TOC=2,3] 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](http://www.php-fig.org/psr/psr-7/#3-2-1-psr-http-message-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(); ~~~ Figure 1: Inject PSR 7 response into application route callback. 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(); ~~~ Figure 2: Inject PSR 7 response into application middleware. ## The Response Status Every HTTP response has a numeric [status code](http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html). 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(); ~~~ Figure 3: Get response status code. You can copy a PSR 7 Response object and assign a new status code like this: ~~~ $newResponse = $response->withStatus(302); ~~~ Figure 4: Create response with new status code. ## 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(", ", $values); } ~~~ Figure 5: Fetch and iterate all HTTP response headers as an associative array. ### Get One Header You can get a single header’s value(s) with the PSR 7 Response object’s `getHeader($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 = $response->getHeader('Vary'); ~~~ Figure 6: Get values for a specific HTTP header. You may also fetch a comma-separated string with all values for a given header with the PSR 7 Response object’s `getHeaderLine($name)` method. Unlike the `getHeader($name)` method, this method returns a comma-separated string. ~~~ $headerValueString = $response->getHeaderLine('Vary'); ~~~ Figure 7: Get single header's values as comma-separated string. ### Detect Header You can test for the presence of a header with the PSR 7 Response object’s`hasHeader($name)` method. ~~~ if ($response->hasHeader('Vary')) { // Do something } ~~~ Figure 8: Detect presence of a specific HTTP header. ### Set Header You can set a header value with the PSR 7 Response object’s `withHeader($name, $value)`method. ~~~ $newResponse = $oldResponse->withHeader('Content-type', 'application/json'); ~~~ Figure 9: Set HTTP header Reminder The Response object is immutable. This method returns a *copy* of the Response object that has the new header value. This method is destructive, and it *replaces* existing header values already associated with the same header name. ### Append Header You can append a header value with the PSR 7 Response object’s `withAddedHeader($name, $value)` method. ~~~ $newResponse = $oldResponse->withAddedHeader('Allow', 'PUT'); ~~~ Figure 10: Append HTTP header Reminder Unlike the `withHeader()` method, this method *appends* the new value to the set of values that already exist for the same header name. The Response object is immutable. This method returns a *copy* of the Response object that has the appended header value. ### Remove Header You can remove a header with the Response object’s `withoutHeader($name)` method. ~~~ $newResponse = $oldResponse->withoutHeader('Allow'); ~~~ Figure 11: Remove HTTP header Reminder The Response object is immutable. This method returns a *copy* of the Response object that has the appended header value. ## 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 = $response->getBody(); ~~~ Figure 12: Get HTTP response body The resultant `\Psr\Http\Message\StreamInterface` instance provides the following methods to read from, iterate, and write to its underlying PHP `resource`. * `getSize()` * `tell()` * `eof()` * `isSeekable()` * `seek()` * `rewind()` * `isWritable()` * `write($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'); ~~~ Figure 13: Write content to the HTTP response body 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); ~~~ Figure 13: Replace the HTTP response body Reminder The Response object is immutable. This method returns a *copy* of the Response object that contains the new body.