foo.php

<?php

/** @private */
class _LinkedListNode {
    private $value;
    private $next;
    public function __construct($this->value, _LinkedListNode $this->next = null);
}

class LinkedList {
    private function makeNode($value, $next) {
        return new class {
            private $value;
            private $next;
            public function __construct($this->value, $this->next = null);
        } ($value, $next);
    }
}