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03.

The HTTP Client Service

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We know that Symfony is a collection of a ton of independent, teensy tiny PHP libraries, called "components". We only have a small number of them installed right now, but as we need more features, we'll install more components. In the last tutorial, we installed the serializer component to help us serialize objects into JSON. Head over and open StarshipApiController.php. Down here, hold "cmd" or "control" on a Mac and click this json() method. Here, we have our serializer component. This checks to see if we have this service, and if we do, the serialize() method is called.

Okay, our site is pretty cool, but wouldn't it be much cooler if we... say... rendered the real-time location of the International Space Station (or ISS)? Of course it would! And luckily, a website already exists that shows that information. We'll navigate to wheretheiss.at and... check it out! It looks like the ISS is somewhere over the Pacific Ocean at the moment and - good news - they also have an API that we can use to fetch the ISS's coordinates and print that on our website. How convenient! You can copy this URL and open it in a new tab to see the JSON.

But first, let's check to see if our application already has an HTTP client to help us execute some API requests. Over at your terminal, run:

bin/console debug:autowiring http

And... we do have some HTTP-related services, but no HTTP client. And that's right! We don't have a service in our app that can do HTTP requests yet, but we can install it. To do that, we need the http-client component, which, as the name might suggest, is great at making external HTTP requests. At your terminal, run:

composer require symfony/http-client

If you're wondering where this package name came from, good question! If you search for "symfony http client" in your browser, one of the top results is this Symfony HTTP Client documentation. Under "Installation", you'll find this terminal command, along with some handy information about the component.

Now, back at our terminal, let's run

bin/console debug:autowiring http

and... there's our HttpClient! Now that we have our new service, we can type hint it in our application. But... wait... this didn't install any bundles. If you run

git status

you can see that the only files changed were composer.json and composer.lock. That's okay! What we installed was a pure PHP package, and while it does contain service classes (which are just classes that do work), it doesn't contain any configuration that says:

Hey! I want to have a service called "http_client", which should be an instance of HttpClientInterface, and it should be instantiated with these specific arguments.

So where did this service come from? The answer is FrameworkBundle. Open config/bundles.php. The first bundle here is FrameworkBundle. That's a core Symfony bundle, and it has been in our application since the beginning. This bundle's superpower is watching for newly installed Symfony components and automatically registering their services. Super convenient.

16 lines | config/bundles.php
// ... lines 1 - 2
return [
Symfony\Bundle\FrameworkBundle\FrameworkBundle::class => ['all' => true],
// ... lines 5 - 14
];

Now that we have our new HttpClient, let's put it to work! Open MainController.php and, in homepage(), let's type hint our new service. I'll move this onto multiple lines... write HttpClientInterface... and call it $client.

32 lines | src/Controller/MainController.php
// ... lines 1 - 9
use Symfony\Contracts\HttpClient\HttpClientInterface;
// ... line 11
class MainController extends AbstractController
// ... lines 13 - 14
public function homepage(
// ... line 16
HttpClientInterface $client,
): Response {
// ... lines 19 - 29
}
}

Down here, before the return statement, write $client->. We have a few methods to choose from, so select request(). Inside, write GET, and then we need to send a request to this URL. To save you some time, you can copy this link from the page below this video. Over here, add $response... and below that, write $response->toArray(). That's a handy method that decodes JSON into an array. And finally, we'll add this $issData variable. To see if it's working, we can go ahead and dump($issData) here.

32 lines | src/Controller/MainController.php
// ... lines 1 - 14
public function homepage(
// ... lines 16 - 17
): Response {
// ... lines 19 - 21
$response = $client->request('GET', 'https://api.wheretheiss.at/v1/satellites/25544');
$issData = $response->toArray();
dump($issData);
// ... lines 25 - 29
}
// ... lines 31 - 32

Over in your browser, refresh the homepage and, down here, if you hover over this icon... nice! That's our data! Right beside this is another icon you may have noticed. That's the HTTP Client, and it shows us the total number of requests that were executed on this page. Click this Debug icon to open the Symfony Profiler and inspect it. Our HTTP Client is integrated with the web debug toolbar, and we can see that our request was executed. Awesome!

Back over here, remove the dump() and pass that data to the template.

32 lines | src/Controller/MainController.php
// ... lines 1 - 14
public function homepage(
// ... lines 16 - 17
): Response {
// ... lines 19 - 24
return $this->render('main/homepage.html.twig', [
// ... lines 26 - 27
'issData' => $issData,
]);
}
// ... lines 31 - 32

In homepage.html.twig, down here at the end, add another <div>. Inside, add an <h2>, and let's call it ISS Location. We'll also add some classes to make it look nice. Okay, down here, let's add some <p> tags with our data: Time: {{ issData.timestamp|date }}, Altitude: {{ issData.altitude }}, Latitude: {{ issData.latitude }}, Longitude: {{ issData.longitude }}, and Visibility: {{ issData.visibility }}.

67 lines | templates/main/homepage.html.twig
// ... lines 1 - 4
{% block body %}
<main class="flex flex-col lg:flex-row">
// ... lines 7 - 8
<div class="px-12 pt-10 w-full">
// ... lines 10 - 54
<div>
<h2 class="text-4xl font-semibold my-8">ISS Location</h2>
<p>Time: {{ issData.timestamp|date }}</p>
<p>Altitude: {{ issData.altitude }}</p>
<p>Latitude: {{ issData.latitude }}</p>
<p>Longitude: {{ issData.longitude }}</p>
<p>Visibility: {{ issData.visibility }}</p>
</div>
</div>
</main>
{% endblock %}

Back at our browser, refresh and... here it is! This is the real-time location of the International Space Station with all of the data we just rendered! Looking good!

As cool as this is, now every time someone navigates to our homepage, we're making an HTTP request to the API, and HTTP requests are slow. To fix that, let's leverage another Symfony service - the cache service.