some weird ass PHP code

test.php

<?php
new class {
    private $foo;
    private $bar;

    public function __construct()
    {
        $this->bar = function(int $id, array $elems) {
            print $id;
        };

        $this->foo = function(...$args) {
            ($this->bar)(...$args);
        };

        ($this->foo)(123, ['elem']);
    }
};