The Closure Puzzle

closure-puzzle.php

<?php
class Bar {
    public function A()
    {
        echo __METHOD__, PHP_EOL;
    }
    
    private function B()
    {
        echo __METHOD__, PHP_EOL;
    }
}

class Bat {
    public function __call($function, $args)
    {
        $bar = new Bar();
        if (is_callable(array($bar, $function))) {
            $bar->{$function}();
        } else {
            $closure = function() use ($function, $bar) {
                $bar->{$function}();
                $this->C();
                $this->D();
            };
            
            $bustOO = Closure::bind($closure, $this, $bar);
            
            $bustOO();
        }
    }
    
    public function C()
    {
        echo __METHOD__, PHP_EOL;
    }
    
    private function D()
    {
        echo __METHOD__, PHP_EOL;
    }
}

$bat = new Bat();
$bat->A();
$bat->B();

closure-this.php

<?php
class Foo {
    public function A()
    {
        $closure = function () {
            $this->B();
        };

        $closure(); // Foo::B
    }

    public function B()
    {
        echo __METHOD__, PHP_EOL;
    }
}

results.txt

$ php closure-puzzle.php 
Bar::A
Bar::B
Bat::C

Fatal error: Call to undefined method Bar::D()