Added chapter on creating PSR-7 clients

doc/book/psr7-clients.md

@@ -0,0 +1,90 @@
+# Using PSR-7 Clients
+
+As noted in the previous section, you can [substitute your own HTTP client by implementing the ClientInterface](http-clients.md#clientinterface-and-headerawareclientinterface).
+In this section, we'll demonstrate doing so in order to use a client that is
+[PSR-7](http://www.php-fig.org/psr/psr-7/)-capable.
+
+## Responses
+
+zend-feed provides a facility to assist with generating a
+`Zend\Feed\Reader\Response` from a PSR-7 `ResponseInterface` via
+`Zend\Feed\Reader\Http\Psr7ResponseDecorator`. As such, if you have a
+PSR-7-capable client, you can pass the response to this decorator, and
+immediately return it from your custom client:
+
+```php
+return new Psr7ResponseDecorator($psr7Response);
+```
+
+We'll do this with our PSR-7 client.
+
+## Guzzle
+
+[Guzzle](http://docs.guzzlephp.org/en/latest/) is arguably the most popular HTTP
+client library for PHP, and fully supports PSR-7 since version 5. Let's install
+it:
+
+```bash
+$ composer require guzzlehttp/guzzle
+```
+
+We'll use the `GuzzleHttp\Client` to make our requests to feeds.
+
+## Creating a client
+
+From here, we'll create our client. To do this, we'll create a class that:
+
+- implements `Zend\Feed\Reader\Http\ClientInterface`
+- accepts a `GuzzleHttp\ClientInterface` to its constructor
+- uses the Guzzle client to make the request
+- returns a zend-feed response decorating the actual PSR-7 response
+
+The code looks like this:
+
+```php
+use GuzzleHttp\Client;
+use GuzzleHttp\ClientInterface as GuzzleClientInterface;
+use Zend\Feed\Reader\Http\ClientInterface as FeedReaderHttpClientInterface;
+use Zend\Feed\Reader\Http\Psr7ResponseDecorator;
+
+class GuzzleClient implements FeedReaderHttpClientInterface
+{
+    /**
+     * @var GuzzleClientInterface
+     */
+    private $client;
+
+    /**
+     * @param GuzzleClientInterface|null $client
+     */
+    public function __construct(GuzzleClientInterface $client = null)
+    {
+        $this->client = $client ?: new Client();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function get($uri)
+    {
+        return new Psr7ResponseDecorator(
+			$this->client->request('GET', $uri)
+		);
+    }
+}
+```
+
+## Using the client
+
+In order to use our new client, we need to tell `Zend\Feed\Reader\Reader` about
+it:
+
+```php
+Zend\Feed\Reader\Reader::setHttpClient(new GuzzleClient());
+```
+
+From this point forward, this custom client will be used to retrieve feeds.
+
+## References
+
+This chapter is based on [a blog post by Stefan Gehrig](https://www.teqneers.de/2016/05/zendfeedreader-guzzle-and-psr-7/).

mkdocs.yml

@@ -6,6 +6,7 @@ pages:
     - Reader:
         - "Zend\\Feed\\Reader": reader.md
         - 'HTTP Clients': http-clients.md
+        - 'Using PSR-7 Clients': psr7-clients.md
         - 'Importing Feeds': importing.md
         - 'Feed Discovery': find-feeds.md
         - 'Consuming RSS Feeds': consuming-rss.md