Delete middle node from linked list in php

Php program for Delete middle node from linked list. Here problem description and explanation.

<?php
/*
    Php program for
    Delete middle node of linked list
*/
// Linked list node
class LinkNode
{
	public $data;
	public $next;
	public	function __construct($data)
	{
		$this->data = $data;
		$this->next = NULL;
	}
}

class SingleLL
{
	public $head;
	public	function __construct()
	{
		$this->head = NULL;
	}
	// Adding new node at beginning of linked list
	public	function addNode($data)
	{
		// Create new node
		$node = new LinkNode($data);
		// Connect current node to previous head
		$node->next = $this->head;
		$this->head = $node;
	}
	// Display linked list element
	public	function display()
	{
		if ($this->head == NULL)
		{
			return;
		}
		$temp = $this->head;
		// iterating linked list elements
		while ($temp != NULL)
		{
			// Display node value
			printf("%s", strval($temp->data).
				" → ");
			// Visit to next node
			$temp = $temp->next;
		}
		printf("%s", " NULL\n");
	}
	// Delete the middle node of linked list
	public	function deleteMid()
	{
		if ($this->head == NULL)
		{
			// When linked list are no elements
			printf("%s\n", "Empty Linked List");
		}
		else if ($this->head->next == NULL && 
                 $this->head->next->next == NULL)
		{
			// When linked list are less than  of 3 nodes
			printf("%s\n", "Less then 3 node of linked list");
		}
		else
		{
			$temp = $this->head;
			$midPrevious = NULL;
			// Find the middle and its previous node
			while ($temp != NULL && $temp->next != NULL && 
                   $temp->next->next != NULL)
			{
				if ($midPrevious == NULL)
				{
					// When first node
					$midPrevious = $temp;
				}
				else
				{
					// Visit to next node
					$midPrevious = $midPrevious->next;
				}
				// Visit to next second next node
				$temp = $temp->next->next;
			}
			// Get the node which is deleting 
			$temp = $midPrevious->next;
			// Show deleted node
			printf("%s\n", "Delete node : ".strval($temp->data));
			// Change link
			$midPrevious->next = $temp->next;
		}
	}
	public static
	function main($args)
	{
		$sll = new SingleLL();
		// Linked list
		// 7 → 6 → 5 → 4 → 3 → 2 → 1 → NULL
		$sll->addNode(1);
		$sll->addNode(2);
		$sll->addNode(3);
		$sll->addNode(4);
		$sll->addNode(5);
		$sll->addNode(6);
		$sll->addNode(7);
		printf("%s\n", "Before Delete middle node");
		$sll->display();
		// Delete middle node
		$sll->deleteMid();
		printf("%s\n", "After Delete middle node");
		$sll->display();
	}
}
SingleLL::main(array());

Output

Before Delete middle node
7 → 6 → 5 → 4 → 3 → 2 → 1 →  NULL
Delete node : 4
After Delete middle node
7 → 6 → 5 → 3 → 2 → 1 →  NULL