Files that live inside your application's config/ directory must use kebab-case.


Within these files, configuration keys must use snake_case.

// config/my-config-file.php
return [
    'my_config_key' => env('CONFIG_KEY'),

You must not use the env() helper outside of the configuration files. In production deployments, the configuration is cached (using php artisan config:cache), and any calls to the env() helper outside of your configuration will return null.

Create a corresponding configuration value for the env() variable, and be sure to include it in the application's .env.example file.