anonymous.php

<?php

interface Logger {
    public function log(string $msg);
 }

 class Application {
    private $logger;

    public function getLogger(): Logger {
       return $this->logger;
    }

    public function setLogger(Logger $logger) {
       $this->logger = $logger;
    }  
 }

 $app = new Application;
 $app->setLogger(new class implements Logger {
    public function log(string $msg) {
       print($msg);
    }
 });

 $app->getLogger()->log("My first Log Message");