class Registry { private static $instance = null; private $data = array(); private function __construct() {} public static function getInstance() { if(self::$instance == null) { self::$instance = new Registry(); } return self::$instance; } public function set($key, $value) { $this->data[$key] = $value; } public function get($key) { return $this->data[$key]; } }In this example, the Registry class contains a private $data array to hold key-value pairs, and a public set and get method to manipulate the registry data. The getInstance method is also implemented as a static method that creates a single instance of the registry if it does not exist, and returns it if it does. A typical use case for the Registry class is to store application settings, such as database credentials or API keys, that are needed by multiple components of an application. This code example belongs to a package/library for creating application-level settings and managing data across various components of an application.