Find second last element of linked list in php

Php program for Find second last element of linked list. Here more information.

<?php
// Php program for
// Find the second last node of a linked list

// Node of Linked List
class LinkNode
{
	public $data;
	public $next;
	public	function __construct($data)
	{
		// Set node value
		$this->data = $data;
		$this->next = NULL;
	}
}
class SingleLL
{
	public $head;
	public $tail;
	public	function __construct()
	{
		$this->head = NULL;
		$this->tail = NULL;
	}
	// Add new node at the end of linked list
	public	function insert($value)
	{
		// Create a new node
		$node = new LinkNode($value);
		if ($this->head == NULL)
		{
			$this->head = $node;
		}
		else
		{
			$this->tail->next = $node;
		}
		$this->tail = $node;
	}
	// Display linked list element
	public	function display()
	{
		if ($this->head == NULL)
		{
			return;
		}
		$temp = $this->head;
		// iterating linked list elements
		while ($temp != NULL)
		{
			echo strval($temp->data).
			" → ";
			// Visit to next node
			$temp = $temp->next;
		}
		echo "null\n";
	}
	//Find the second last node of a linked list
	public	function secondLast()
	{
		$node = $this->head;
		if ($node == NULL)
		{
			echo "Empty linked list\n";
		}
		else if ($node->next == NULL)
		{
			echo "Only one node in this linked list\n";
		}
		else
		{
			// Find second last node
			while ($node->next != NULL && $node->next->next != NULL)
			{
				// Visit to second next node
				$node = $node->next->next;
			}
			printf("Second last element is : %d\n",$node->data);
		}
	}
	public static
	function main($args)
	{
		$sll = new SingleLL();
		// Add linked list node
		$sll->insert(6);
		$sll->insert(3);
		$sll->insert(2);
		$sll->insert(7);
		$sll->insert(1);
		$sll->insert(9);
		echo "Linked List\n";
		// 6 → 3 → 2 → 7 → 1 → 9 → null
		$sll->display();
		$sll->secondLast();
	}
}
SingleLL::main(array());

Output

Linked List
6 → 3 → 2 → 7 → 1 → 9 → null
Second last element is : 1