composer-psr-4-autoloader

Composer & PSR-4 Autoloader

In the last lesson, we created a simple custom autoloader. It loads the files in the Framework folder and then we can instantiate the classes. However, this will not work if we have sub-folders and namespaces, which we will get into in the next lesson.

We could refactor the autoloader to handle this, but there is a standard called PSR-4 that we can use. This is a standard for autoloading classes. It is used by many frameworks and libraries.

Composer

PHP has a package manager called Composer. It is similar to **NPM **for Node.js. It allows us to install packages and libraries from the command line. It also has a built-in autoloader that we can use. This autoloader will follow the PSR-4 standard.

To install Composer, go to https://getcomposer.org/download/ and follow the instructions for your operating system.

Once installed, you can run composer in the terminal to see a list of commands.

Composer Autoloader

Now we can use the Composer autoloader. First, we need to create a composer.json file in the root of our project. This file will contain our project information and dependencies. We can also configure our autoloader and namespaces here.

Add the following to the composer.json file`:

{
  "name": "bradtraversy/workopia",
  "description": "Job listing application",
  "authors": [
    {
      "name": "Brad Traversy",
      "email": "traversymedia@gmail.com"
    }
  ],
  "autoload": {
    "psr-4": {
      "Framework\\": "Framework/",
      "App\\": "App/"
    }
  }
}

Replace the name and email with your own. The package name also needs to be unique. You can use your GitHub username and the project name.

In the autoload section, we are defining our namespaces and the folders they are in. So anything in the Framework folder will use the Framework namespace and anything in the App folder will use the App namespace. Again, we will get more into namespaces in the next video.

Now we can install the Composer autoloader by running composer install in the terminal. This will create a vendor folder and a composer.lock file. The vendor folder will contain the autoloader and any packages we install. You almost never want to edit anything in the vendor folder. If you are familiar with the JavaScript world, think of it as the node_modules folder.

Include Autoloader

We need to include our autoloader.

In the public/index.php file, add the following to the top of the file:

require __DIR__ . '/../vendor/autoload.php';

The __DIR__ magic constant will give us the absolute path to the public folder. We then go up one directory and into the vendor folder and then include the autoload.php file. We should actually use this for the helpers.php file as well.

So these should be the first two lines after the opening PHP tag:

require __DIR__ . '/../vendor/autoload.php';
require __DIR__ . '/../helpers.php';

Now if you go to your application, it will be broken because it is looking for the namespaces Framework and App and we have not created those yet. We will do that in the next lesson.