First of all, be sure to define the classes discussed in the previous two recipes. After that, you can create another simple server program, chap_09_middleware_server_with_response.php, which sets up autoloading and uses the appropriate classes:

<?php
require __DIR__ . '/../Application/Autoload/Loader.php';
Application\Autoload\Loader::init(__DIR__ . '/..');
use Application\MiddleWare\ { Constants, ServerRequest, Response, Stream };

You can then define an array with key/value pairs, where the value points to a text file in the current directory to be used as content:

$data = [
  1 => 'churchill.txt',
  2 => 'gettysburg.txt',
  3 => 'star_trek.txt'
];

Next, inside a try...catch block, you can initialize some variables, initialize the server request, and set up a temporary filename:

try {

    $body['text'] = 'Initial State';
    $request = new ServerRequest();
    $request->initialize();
    $tempFile = bin2hex(random_bytes(8)) . '.txt';
    $code = 200;

After that, check to see whether the method is GET or POST. If it's GET, check to see whether an id parameter was passed. If so, return the body of the matching text file. Otherwise, return a list of text files:

if ($request->getMethod() == Constants::METHOD_GET) {
    $id = $request->getQueryParams()['id'] ?? NULL;
    $id = (int) $id;
    if ($id && $id <= count($data)) {
        $body['text'] = file_get_contents(
        __DIR__ . '/' . $data[$id]);
    } else {
        $body['text'] = $data;
    }

Otherwise, return a response indicating a success code 204 and the size of the request body received:

} elseif ($request->getMethod() == Constants::METHOD_POST) {
    $size = $request->getBody()->getSize();
    $body['text'] = $size . ' bytes of data received';
    if ($size) {
        $code = 201;
    } else {
        $code = 204;
    }
}

You can then catch any exceptions and report them with a status code of 500:

} catch (Exception $e) {
    $code = 500;
    $body['text'] = 'ERROR: ' . $e->getMessage();
}

The response needs to be wrapped in a stream, so you can write the body out to the temp file and create it as Stream. You can also set the Content-Type header to application/json and run getHeaders(), which outputs the current set of headers. After that, echo the body of the response. For this illustration, you could also dump the Response instance to confirm it was constructed correctly:

try {
    file_put_contents($tempFile, json_encode($body));
    $body = new Stream($tempFile);
    $header[Constants::HEADER_CONTENT_TYPE] = 'application/json';
    $response = new Response($code, $body, $header);
    $response->getHeaders();
    echo $response->getBody()->getContents() . PHP_EOL;
    var_dump($response);

To wrap things up, catch any errors or exceptions using Throwable, and don't forget to delete the temp file:

} catch (Throwable $e) {
    echo $e->getMessage();
} finally {
   unlink($tempFile);
}

To test, it's just a matter of opening a terminal window, changing to the /path/to/source/for/this/chapter directory, and running the following command:

php -S localhost:8080

From a browser, you can then call this program, adding an id parameter. You might consider opening the developer tools to monitor the response header. Here is an example of the expected output. Note the content type of application/json: