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> Symfony 4 > Symfony 4 Fundamentals: Services, Config & Environments
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07.

Leveraging the prod Environment

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Right now, our app is in the dev environment. How can we change it to prod? Just open .env and set APP_ENV to prod!

# .env

# ...
APP_ENV=prod
# ...

Then... refresh!

This page may or may not work for you. One big difference between the dev and prod environments is that in the prod environment, the internal Symfony cache is not automatically rebuilt. That's because the prod environment is wired for speed.

In practice, this means that whenever you want to switch to the prod environment... like when deploying... you need to run a command:

./bin/console cache:clear

The bin/console file also reads the .env file, so it knows we're in the prod environment.

And now when we refresh, it should definitely work. And check it out! There's no web debug toolbar. And if you go to a fake page, you get a very boring error page. And yea, you can totally customize this: just Google for "Symfony error pages": it's really easy. The point is, this is not a big development exception page anymore.

Click back into our article, and then go find its template: show.html.twig. Let's change the 3 hours ago to 4 hours ago:

83 lines | templates/article/show.html.twig
// ... lines 1 - 4
{% block body %}
<div class="container">
<div class="row">
<div class="col-sm-12">
<div class="show-article-container p-3 mt-4">
<div class="row">
<div class="col-sm-12">
// ... line 13
<div class="show-article-title-container d-inline-block pl-3 align-middle">
// ... lines 15 - 17
<span class="pl-2 article-details"> 4 hours ago</span>
// ... lines 19 - 22
</div>
</div>
</div>
// ... lines 26 - 71
</div>
</div>
</div>
</div>
{% endblock %}
// ... lines 78 - 83

Move back to your browser and refresh! Yep! The page did not update! That's the behavior I was talking about.

To make it update, find your terminal and run:

./bin/console cache:clear

The dev and prod Cache Directories

Oh, and check out the var/cache directory. Each environment has its own cache directory: dev and prod. When you run cache:clear, it basically just clears the directory and recreates a few files. But there is another command:

./bin/console cache:warmup

This goes a step further and creates all of the cache files that Symfony will ever need. By running this command when you deploy, the first requests will be much faster. Heck, you can even deploy to a read-only filesystem!

And now when you refresh... it works: 4 hours ago.

Changing the Cache in the dev Environment

Change the environment back to dev:

# .env

# ...
APP_ENV=dev
# ...

Here's our next challenge. In config/packages/framework.yaml, we configured the cache to use APCu:

31 lines | config/packages/framework.yaml
framework:
// ... lines 2 - 16
cache:
// ... lines 18 - 28
# APCu (not recommended with heavy random-write workloads as memory fragmentation can cause perf issues)
app: cache.adapter.apcu

What if we did want to use this for production, but in the dev environment, we wanted to use the filesystem cache instead for simplicity. How could we do that?

We already know the answer! We just need to override this key inside the dev environment. Create a new file in config/packages/dev called framework.yaml... though technically, this could be called anything. We just need the same keys: framework, cache, app. Add those, but now set app to cache.adapter.filesystem, which was the original value:

4 lines | config/packages/dev/framework.yaml
framework:
cache:
app: cache.adapter.filesystem

Let's see if it worked! Open ArticleController and dump the $cache object so we can see what it looks like:

82 lines | src/Controller/ArticleController.php
// ... lines 1 - 13
class ArticleController extends AbstractController
{
// ... lines 16 - 26
public function show($slug, MarkdownInterface $markdown, AdapterInterface $cache)
{
// ... lines 29 - 53
dump($cache);die;
// ... lines 55 - 67
}
// ... lines 69 - 80
}

And, refresh! Yes! It's using the FilesystemAdapter! What about the prod environment? In .env, change APP_ENV back to prod:

# .env

# ...
APP_ENV=prod
# ...

But don't forget to clear the cache:

./bin/console cache:clear

The warmup part is optional. Refresh! Yea! In the prod environment, the cache still uses APCu.

Change the environment back to dev:

# .env

# ...
APP_ENV=dev
# ...

In reality, you won't spend much time in the prod environment... it mostly exists for when you deploy to production.

Let's also remove the dump():

82 lines | src/Controller/ArticleController.php
// ... lines 1 - 13
class ArticleController extends AbstractController
{
// ... lines 16 - 26
public function show($slug, MarkdownInterface $markdown, AdapterInterface $cache)
{
// ... lines 29 - 53
dump($cache);die;
// ... lines 55 - 67
}
// ... lines 69 - 80
}

Oh man, with environments behind us, we can jump into the heart of our tutorial.. the thing I have been waiting to do: create our own services.