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Bootstrapping the Bundle & Autoloading

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Heeeeey Symfony peeps! I'm excited! Because we're going to dive deep in to a super interesting topic: how to create your own bundles. This is useful if you need to share code between your own projects. Or if you want to share your great new open source library with the whole world. Actually, forget that! This tutorial is going to be awesome even if you don't need to do either of those. Why? Because we use third-party bundles every day. And by learning how to create one, we're going to become experts in how they work and really get a look at Symfony under the hood.

As always, you can earn free high-fives by downloading the source code from this page and coding along with me. After unzipping the file, you'll find a start/ directory with the same code that you see here. Follow the file for steps on how to get your project setup.

The last step will be to open a terminal, move into the project, sip your coffee, and run:

php bin/console server:run

to start the built-in PHP web server.

Introducing KnpUIpsum

Head to your browser and go to http://localhost:8000. Say hello to The Space Bar! This is a Symfony application - the one we're building in our beginner Symfony series. Click into one of the articles to see a bunch of delightful, fake text that we're using to make this page look real. Each time you refresh, you get new random, happy content.

To find out where this is coming from, in the project, open src/Service/KnpUIpsum.php. Yes! This is our new creation: it returns "lorem ipsum" dummy text, but with a little KnpUniversity flare: the classic latin is replaced with rainbows, unicorns, sunshine and more of our favorite things.

340 lines | src/Service/KnpUIpsum.php
// ... lines 1 - 2
namespace App\Service;
// ... lines 4 - 9
class KnpUIpsum
private $unicornsAreReal;
private $minSunshine;
public function __construct(bool $unicornsAreReal = true, $minSunshine = 3)
$this->unicornsAreReal = $unicornsAreReal;
$this->minSunshine = $minSunshine;
* Returns several paragraphs of random ipsum text.
* @param int $count
* @return string
public function getParagraphs(int $count = 3): string
$paragraphs = array();
for ($i = 0; $i < $count; $i++) {
$paragraphs[] = $this->addJoy($this->getSentences($this->gauss(5.8, 1.93)));
return implode("\n\n", $paragraphs);
// ... lines 37 - 338

And, you know what? I think we all deserve more cupcakes, kittens & baguettes in our life. So I want to share this functionality with the world, by creating the KnpULoremIpsumBundle! Yep, we're going to extract this class into its own bundle, handle configuration, add tests, and do a bunch of other cool stuff.

Right now, we're using this code inside of ArticleController: it's being passed to the constructor. Below, we use that to generate the content.

77 lines | src/Controller/ArticleController.php
// ... lines 1 - 2
namespace App\Controller;
// ... lines 4 - 14
class ArticleController extends AbstractController
* Currently unused: just showing a controller with a constructor!
private $isDebug;
private $knpUIpsum;
public function __construct(bool $isDebug, KnpUIpsum $knpUIpsum)
$this->isDebug = $isDebug;
$this->knpUIpsum = $knpUIpsum;
* @Route("/", name="app_homepage")
public function homepage()
return $this->render('article/homepage.html.twig');
// ... lines 37 - 75

Isolating into a new Bundle Directory

Ok, the first step to creating a new bundle is to move this code into its own location. Eventually, all the code for the bundle will live in its own completely separate directory & repository. But, sometimes, when you first start building, it's a bit easier to keep the code in your project: it let's you hack on things really quickly & test them in your app.

So let's keep the code here for now, but isolate it from the app's code. To do that, create a new lib/ directory. And then, another called LoremIpsumBundle: this will be the temporary home for our shiny bundle. Inside, there are a few valid ways to organize things, but I like to create a src/ directory.

mkdir lib
mkdir lib/LoremIpsumBundle
mkdir lib/LoremIpsumBundle/src


You can also just type one command instead of three:

mkdir -p lib/LoremIpsumBundle/src

Perfect! Now, move the KnpUIpsum class into that directory. And yea, you could put this into a src/Service directory, or anywhere else you want.

New Vendor Namespace

Oh, but this namespace will not work anymore. We need a namespace that's custom to our bundle. It could be anything, but usually it has a vendor part - like KnpU and then the name of the library or bundle - LoremIpsumBundle.

340 lines | lib/LoremIpsumBundle/src/KnpUIpsum.php
// ... lines 1 - 2
namespace KnpU\LoremIpsumBundle;
// ... lines 4 - 9
class KnpUIpsum
// ... lines 11 - 340

And, that's it! If we had decided to put KnpUIpsum into a sub-directory, like Service, then we would of course also add Service to the end of the namespace like normal.

Next, back in ArticleController, go up to the top, remove the use statement, and re-type it to get the new one.

77 lines | src/Controller/ArticleController.php
// ... lines 1 - 2
namespace App\Controller;
// ... line 4
use KnpU\LoremIpsumBundle\KnpUIpsum;
// ... lines 6 - 77

Handling Autoloading

So... will it work! Yea... probably not - but let's try it! Nope! But I do love error messages:

Cannot autowire ArticleController argument $knpUIpsum... because the KnpUIpsum class was not found.

Of course! After creating the new lib/ directory, we need to tell Composer's autoloader to look for the new classes there. Open composer.json, find the autoload section, and add a new entry: the KnpU\\LoremIpsumBundle\\ namespace will live in lib/LoremIpsumBundle/src/.

77 lines | composer.json
// ... lines 1 - 36
"autoload": {
"psr-4": {
"KnpU\\LoremIpsumBundle\\": "lib/LoremIpsumBundle/src/",
// ... line 40
// ... lines 43 - 77

Then, open a new terminal tab. To make the autoload changes take effect, run:

composer dump-autoload

Registering the Service

Will it work now? Try it! Bah, not yet: but we're closer. The error changed: instead of "class not found", now it says that no KnpUIpsum service exists. To solve this, open config/services.yaml.

Thanks to the auto-registration code in here, we don't normally need to register our classes as services: that's automatic. But, it's only automatic for classes that live in src/. Yep, as soon as we moved the class from src/ to lib/, that service disappeared.

And that's ok! When you create a re-usable bundle, you actually don't want to rely on auto-registration or autowiring. Instead, as a best-practice, you should configure everything explicitly to avoid any surprises.

To do that, at the bottom of this file, add KnpU\LoremIpsumBundle\KnpUIpsum: ~.

39 lines | config/services.yaml
// ... lines 1 - 5
// ... lines 7 - 37
KnpU\LoremIpsumBundle\KnpUIpsum: ~


If you're on Symfony 4.4 or higher, you can remove this KnpU\LoremIpsumBundle\KnpUIpsum: ~ configuration line from the config/services.yaml file.

This adds a new service for that class. And because we don't need to pass any options or arguments, we can just set this to ~. The class does have constructor arguments, but they have default values.

Ok, try it again! Yes! It finally works! We've successfully isolated our code into its own directory and we are ready to hack! Next, let's make this a bundle with a bundle class and start digging into how bundles can automatically register services.