class Logger { private static $instance = null; private function __construct() {} public static function getInstance() { if (self::$instance == null) { self::$instance = new Logger(); } return self::$instance; } public function log($message) { // logic to write message to log file } }In the above code, the `Logger` class has a private constructor, which means that it cannot be instantiated from outside the class. The `getInstance` method is a public static method that checks whether an instance of the class exists or not. If an instance does not exist, it creates a new instance of the class and returns it. If an instance already exists, it returns the existing instance. The `log` method is a simple method that writes a message to a log file. Once you have created an instance of the Logger class, you can call the `log` method to write messages to the log file. Based on the code example above, the `Logger` class is part of a custom package or library rather than the standard PHP library.