Organizing Your Business Logic

Storing Classes Outside of the Bundle?

But there's no technical reason for putting business logic inside of a bundle. If you like, you can create your own namespace inside the src/ directory and put things there:

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symfony-project/
├─ app/
├─ src/
│  ├─ Acme/
│  │   └─ Utils/
│  │      └─ MyClass.php
│  └─ AppBundle/
├─ vendor/
└─ web/

Services: Naming and Format

The blog application needs a utility that can transform a post title (e.g. "Hello World") into a slug (e.g. "hello-world"). The slug will be used as part of the post URL.

Let's create a new Slugger class inside src/AppBundle/Utils/ and add the following slugify() method:

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// src/AppBundle/Utils/Slugger.php
namespace AppBundle\Utils;

class Slugger
{
    public function slugify($string)
    {
        return preg_replace(
            '/[^a-z0-9]/', '-', strtolower(trim(strip_tags($string)))
        );
    }
}

Next, define a new service for that class.

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# app/config/services.yml
services:
    # keep your service names short
    app.slugger:
        class: AppBundle\Utils\Slugger

Traditionally, the naming convention for a service involved following the class name and location to avoid name collisions. Thus, the service would have been called app.utils.slugger. But by using short service names, your code will be easier to read and use.

Now you can use the custom slugger in any controller class, such as the AdminController:

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public function createAction(Request $request)
{
    // ...

    if ($form->isSubmitted() && $form->isValid()) {
        $slug = $this->get('app.slugger')->slugify($post->getTitle());
        $post->setSlug($slug);

        // ...
    }
}

Service Format: YAML

In the previous section, YAML was used to define the service.

This is controversial, and in our experience, YAML and XML usage is evenly distributed among developers, with a slight preference towards YAML. Both formats have the same performance, so this is ultimately a matter of personal taste.

We recommend YAML because it's friendly to newcomers and concise. You can of course use whatever format you like.

Service: No Class Parameter

You may have noticed that the previous service definition doesn't configure the class namespace as a parameter:

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# app/config/services.yml

# service definition with class namespace as parameter
parameters:
    slugger.class: AppBundle\Utils\Slugger

services:
    app.slugger:
        class: '%slugger.class%'

This practice is cumbersome and completely unnecessary for your own services.

This practice was wrongly adopted from third-party bundles. When Symfony introduced its service container, some developers used this technique to easily allow overriding services. However, overriding a service by just changing its class name is a very rare use case because, frequently, the new service has different constructor arguments.

Using a Persistence Layer

Symfony is an HTTP framework that only cares about generating an HTTP response for each HTTP request. That's why Symfony doesn't provide a way to talk to a persistence layer (e.g. database, external API). You can choose whatever library or strategy you want for this.

In practice, many Symfony applications rely on the independent Doctrine project to define their model using entities and repositories. Just like with business logic, we recommend storing Doctrine entities in the AppBundle.

The three entities defined by our sample blog application are a good example:

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symfony-project/
├─ ...
└─ src/
   └─ AppBundle/
      └─ Entity/
         ├─ Comment.php
         ├─ Post.php
         └─ User.php

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namespace AppBundle\Entity;

use Doctrine\ORM\Mapping as ORM;
use Doctrine\Common\Collections\ArrayCollection;

/**
 * @ORM\Entity
 */
class Post
{
    const NUMBER_OF_ITEMS = 10;

    /**
     * @ORM\Id
     * @ORM\GeneratedValue
     * @ORM\Column(type="integer")
     */
    private $id;

    /**
     * @ORM\Column(type="string")
     */
    private $title;

    /**
     * @ORM\Column(type="string")
     */
    private $slug;

    /**
     * @ORM\Column(type="text")
     */
    private $content;

    /**
     * @ORM\Column(type="string")
     */
    private $authorEmail;

    /**
     * @ORM\Column(type="datetime")
     */
    private $publishedAt;

    /**
     * @ORM\OneToMany(
     *      targetEntity="App\Entity\Comment",
     *      mappedBy="post",
     *      orphanRemoval=true
     * )
     * @ORM\OrderBy({"publishedAt"="ASC"})
     */
    private $comments;

    public function __construct()
    {
        $this->publishedAt = new \DateTime();
        $this->comments = new ArrayCollection();
    }

    // getters and setters ...
}

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$ composer require "doctrine/doctrine-fixtures-bundle"

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use Symfony\Component\HttpKernel\Kernel;

class AppKernel extends Kernel
{
    public function registerBundles()
    {
        $bundles = array(
            // ...
        );

        if (in_array($this->getEnvironment(), array('dev', 'test'))) {
            // ...
            $bundles[] = new Doctrine\Bundle\FixturesBundle\DoctrineFixturesBundle();
        }

        return $bundles;
    }

    // ...
}

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$ php app/console doctrine:fixtures:load

Careful, database will be purged. Do you want to continue Y/N ? Y
  > purging database
  > loading AppBundle\DataFixtures\ORM\LoadFixtures

Coding Standards

The Symfony source code follows the PSR-1 and PSR-2 coding standards that were defined by the PHP community. You can learn more about the Symfony Coding standards and even use the PHP-CS-Fixer, which is a command-line utility that can fix the coding standards of an entire codebase in a matter of seconds.

Next: Controllers