<?php
class Node 
{
    public $data;
    public ?Node $next = null;
}
class LinkedList
{
    private ?Node $head = null;
    
    function addLeft($data)
    {
        $node = new Node();
        $node->data = $data;
        $node->next = $this->head;
        $this->head = $node;
    }
    function removeLeft() 
    {
        if (!$this->head) 
        {
            echo "Linked list empty\n";
            return;
        }
        $data = $this->head->data;
        $this->head = $this->head->next;
        echo $data . " removed\n";
    }
    function reverse()
    {
        $prev = NULL;
        $next = NULL;
        $curr = $this->head;
        
        while ($curr) 
        {
            $next = $curr->next;
            $curr->next = $prev;
            $prev = $curr;
            $curr = $next;
        }
        $this->head = $prev;
    }
}
function main() 
{
    $list = new LinkedList();
    
    $list->addLeft(30);
    $list->addLeft(20);
    $list->addLeft(10);
    print_r($list);
    
    $list->reverse();
    print_r($list);
    
    $list->removeLeft();
    $list->removeLeft();
    $list->removeLeft();
    $list->removeLeft();
    print_r($list);
}
main();