<?php

    class Test extends Thread
    {
        public $callbackVar;

        public function run()
        {
            $this->callbackVar->__invoke();
        }

        public function setClosure(Closure $callback)
        {
            $this->callbackVar = $callback;
        }

        public function setDeclarativeClosure()
        {
            $this->callbackVar = function()
            {
                echo "Declarative closure";
            };
        }

        public function rewrapClosure(Closure $callback)
        {
            $localCallback = function($c)
            {
                $_c = $c;
                return function() use ($_c)
                {
                    $_c();
                };
            };

            $this->callbackVar = $localCallback($callback);
        }
    }

    error_reporting(0);

    $callbackVar = function()
    {
        echo "Callback var invoked.";
    };

    $test = new Test();

    $test->setClosure($callbackVar);
    assert($test->callbackVar === null, 'Callback is not null.');
    $test->callbackVar->__invoke();
    $test->start();

    $test->setDeclarativeClosure();
    assert($test->callbackVar === null, 'Callback is not null.');
    $test->callbackVar->__invoke();
    $test->start();

    $test->rewrapClosure($callbackVar);
    assert($test->callbackVar === null, 'Callback is not null.');
    $test->callbackVar->__invoke();
    $test->start();