This enable you to cherry pick the packages you need to compose your application.

This re-organisation is also a great news for maintainance, as these packages will be released separately, thus allowing more frequent updates.

### **Autoloading** The custom PHP class autoloader have been removed in favor of Composer's PSR-4 implementation. This means that in order for Yii to see your classes, you will have to explicitly register your namespace in `composer.json`. We will see an example later. ### **PSR compatibility** Yii 3 takes some positive steps following the [PHP-FIG](https://www.php-fig.org/) recommendations, by implementing the following PSRs:

* Logging is now compliant with PSR-3* Dependency Injection is now compliant with PSR-11

### **Application configuration** <small>[TODO]</small> ### **Dependencies injection**

<small>[TODO]</small>Let's introduce them briefly:

### **The Framework**

* [yiisoft/yii-core](https://github.com/yiisoft/yii-core)### **Librairies**

In Yii 3, libraries do **not** depend on Yii and are meant to be usable outside the framework.* [yiisoft/db-elasticsearch](https://github.com/yiisoft/db-elasticsearch) Elastic

### **Extensions**

Extensions depends (at least) on yii-core. Aside from the 3 extensions already encountered above (yii-console, yii-web, yii-api), these packages are availableLet's try running a web application using Yii 3, and the provided project template.

##### **Installing the project template**

```> You could start from scratch using this bare template, select the extensions & packages you want to use and start developing, or you can pick one of the three starters provided.

##### **Installing the `web` starter**

Since we're doing a web application, we will need an asset manager. We can pick either one of those:So where do what we see in the browser comes from ?

#####  **Exploring yiisoft/yii-base-web structure:**

If you explore the folder in `vendor/yiisoft/yii-base-web`, you will see that the template is in fact a project itself, with this structure:

```
.