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Config.yml: Control Center for Services

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Ok, I get it: I bring in a bundle and it gives me more useful objects. But, there must be a way for us to configure and control how these services behave, right? Otherwise, how could we control what server the mailer uses for sending emails? Or what if we want to change how the logger works: making it log to a database instead of the default var/logs/dev.log file?

The answer to all of this lies in just one file: app/config/config.yml. That's right: one file is responsible for controlling everything from the log file to the database password. That's pretty powerful: so let's find out how it works!

Other than imports - which loads other files - and parameters - which we'll talk about soon - every root key in this file - like framework, twig and doctrine - corresponds to a bundle that is being configured:

72 lines | app/config/config.yml
- { resource: parameters.yml }
- { resource: security.yml }
- { resource: services.yml }
# Put parameters here that don't need to change on each machine where the app is deployed
# http://symfony.com/doc/current/best_practices/configuration.html#application-related-configuration
locale: en
// ... lines 12 - 35
# Twig Configuration
// ... lines 38 - 42
# Doctrine Configuration
// ... lines 45 - 72

All of this stuff under framework is configuration for the FrameworkBundle:

72 lines | app/config/config.yml
// ... lines 1 - 10
#esi: ~
#translator: { fallbacks: ["%locale%"] }
secret: "%secret%"
resource: "%kernel.root_dir%/config/routing.yml"
strict_requirements: ~
form: ~
csrf_protection: ~
validation: { enable_annotations: true }
#serializer: { enable_annotations: true }
engines: ['twig']
#assets_version: SomeVersionScheme
default_locale: "%locale%"
trusted_hosts: ~
trusted_proxies: ~
# handler_id set to null will use default session handler from php.ini
handler_id: ~
save_path: "%kernel.root_dir%/../var/sessions/%kernel.environment%"
fragments: ~
http_method_override: true
assets: ~
// ... lines 35 - 72

Everything under twig is used to control the behavior of the services from TwigBundle:

72 lines | app/config/config.yml
// ... lines 1 - 35
# Twig Configuration
debug: "%kernel.debug%"
strict_variables: "%kernel.debug%"
// ... lines 40 - 72

The job of a bundle is to give us services. And this is our chance to tweak how those services behave.

Get a big List of all Configuration

That's amazing! Except... how are we supposed to know what keys can live under each of these sections? Documentation of course! There's a great reference section on symfony.com that shows you everything you can control for each bundle.

But I'll show you an even cooler way.

Head back to terminal and use our favorite ./bin/console to run config:dump-reference:

./bin/console config:dump-reference

Actually, there's a shorter version of this called debug:config. This shows us a map with the bundle name on the left and the "extension alias" on the right... that's a fancy way of saying the root config key.


You can also use the shorter: ./bin/console debug:config command.

That's not really that useful. But re-run it with an argument: twig:

./bin/console config:dump-reference twig

Woh! It dumped a giant yml example of everything you can configure under the twig key. Ok, it's not all documented... but honestly, this is usually enough to find what you need.

Playing with Configuration

Ok, lets's experiment! Obviously, the render() function we use in the controller leverages a twig service behind the scenes. Pretend that the number of known species is this big 99999 number and send that through a built-in filter called number_format:

40 lines | app/Resources/views/genus/show.html.twig
// ... lines 1 - 4
{% block body %}
<h2 class="genus-name">{{ name }}</h2>
<div class="sea-creature-container">
<div class="genus-photo"></div>
<div class="genus-details">
<dl class="genus-details-list">
// ... lines 12 - 14
<dd>{{ '99999'|number_format }}</dd>
// ... lines 16 - 17
<div id="js-notes-wrapper"></div>
{% endblock %}
// ... lines 23 - 40

Refresh! That filter gives us a nice, 99,999, formatted-string. But what if we lived in a country that formats using a . instead? Time to panic!!?? Of course not: the bundle that gives us the twig service probably gives us a way to control this behavior.

How? In the config:dump-reference dump, there's a number_format:, thousands_separator key. In config.yml, add number_format: then thousands_separator: '.':

72 lines | app/config/config.yml
// ... lines 1 - 35
# Twig Configuration
// ... lines 38 - 39
thousands_separator: '.'
// ... lines 42 - 72

Behind the scenes, this changes how the service behaves. And when we refresh, that filter gives us 99.999.

If this makes sense, you'll be able to control virtually every behavior of any service in Symfony. And since everything is done with a service... well, that makes you pretty dangerous.

Now, what if you make a typo in this file? Does it just ignore your config? Hmm, try it out: rename this key to thousand_separators with an extra s. Refresh! Boom! A huge error! All of the configuration is validated: if you make a typo, Symfony has your back.