Published Feb 18, 2019 / 2 min read

PSR-4: autoloading and namespaces

• Introduction
• PSR-4 configuration
  • Define root directory
  • Require autoloader
• Use namespaces
• Import files
• Further Resources

A common convention to achieve more structure for your projects is to use 1 file for 1 class. Without require each file over and over again, we can make use of a PSR-4 autoloader. This is a well known standard for PHP projects.

I published an example project on a GitHub repository.

The configuration takes place within the composer.json file. The structure is as follows:

"autoload": {
        // define autoloader standard 
        "psr-4": {
            // define project name and point to
            // your root directory of files
            "Projectname\\":"src"
        }
    }

IMPORTANT: Do not forget to run composer dump-autoload each time you make any chances on the configuration. Else, the chance will not take place.

The root directory is the base directory for all your files. The namespaces will be relative to your defined root directory. Pick as name the name of your project or company.

You need to enable the autoloader at an entry point of your application. A good place would be your index.php. Simply require the autoloader files.

   require 'vendor/autoload.php';

use appropriate namespace for your class files. Those namespaces are relative from the file directory you specified within autoloader config. In our case src

   // for a file within /src
   namespace Projectname;

   // for a file within src/xyz
   namespace Projectname\xyz

In order to use various objects within your files, make sure to import those classes with the use keyword.

// for files within the file root  
use Projectname;
// for files within other pathes
   use Projectname\xyz;