<?php
class Queue {
    public $first, $last;

    public function __construct() {
        $this->last = null;
        $this->first = null;
    }

    public function getList() {
        $curr = $this->last;
        while ($curr != null) {
            yield $curr->data;
            $curr = $curr->next;
        }
    }

    public function contains($node) {
        foreach ($this->getList() as $curr)
            if ($curr == $node)
                return true;
        return false;
    }

    public function put($value) {
        $node = new Node($value);
        if ($this->first == null) {
            $this->first = $node;
            $this->last = $node;
        } else {
            $this->last->next = $node;
            $this->last = $node;
        }
    }

    public function get() {
        if ($this->first == null) return 'Очередь пуста';
        $item = $this->first->data;
        $this->first = $this->first->next;
        return $item;
    }
}