Online PHP editor | output for pG7Ld

<?php interface MyInterface { public function get(): int; public function set(int $value); } class Factory { private $instance = null; public function getInstance(): MyInterface { if ($this->instance === null) { $this->instance = new class() implements MyInterface { private static $instanciated = false; public function __construct() { if (self::$instanciated) { throw new RuntimeException('Could not instanciate class'); } self::$instanciated = true; } private $var; public function get(): int { return $this->var; } public function set(int $value) { $this->var = $value; } }; } return $this->instance; } } function display(MyInterface $object) { var_dump($object->get()); } $factory = new Factory(); $o = $factory->getInstance(); $o->set(5); $o2 = $factory->getInstance(); display($o2);