Description:
------------
---
From manual page: https://php.net/class.closure
---

So, no Singleton in the PHP!

Test script:
---------------
<?php

final class A {
    private function __construct() {}
    private function __clone() {
        throw new \Exception('Singleton');
    }
    private function __sleep() {
        throw new \Exception('Singleton');
    }
    private function __wakeup() {
        throw new \Exception('Singleton');
    }
    public static function instantiate() {
        static $obj;
        return $obj = $obj ?? new self;
    }
}

$closure = function () {
    $class = get_class($this);
    return new $class;
};

$obj = A::instantiate();

var_dump($obj);
var_dump($closure->call($obj));