Convert singly linked list to circular list in php

Php program for Convert singly linked list to circular list. Here problem description and explanation.

<?php
// Php program for
// Convert singly linked list into circular list

// Define class of linked list Node
class LinkNode
{
	public $data;
	public $next;
	public	function __construct($data)
	{
		$this->data = $data;
		$this->next = NULL;
	}
}
class LinkedList
{
	public $head;
	// Class constructor
	public	function __construct()
	{
		$this->head = NULL;
	}
	// Check circular linked list or not
	// Note that this function is not capable to detect loop
	public	function isCircular()
	{
		if ($this->head == NULL)
		{
			// Case when linked list is empty
			return false;
		}
		else
		{
			$temp = $this->head;
			while ($temp != NULL)
			{
				// Visit to next node
				$temp = $temp->next;
				if ($temp == $this->head)
				{
					// When detecting circular node
					return true;
				}
			}
			// When not circular linked list
			return false;
		}
	}
	// Display node element of linked list
	public	function display()
	{
		if ($this->head == NULL)
		{
			echo "Empty Linked List", "\n";
		}
		else
		{
			echo "Linked List Element :";
			$temp = $this->head;
			// Iterate linked list
			while ($temp != NULL)
			{
				// Display node
				echo "  ".strval($temp->data);
				// Visit to next node
				$temp = $temp->next;
				if ($temp == $this->head)
				{
					// Stop iteration
					return;
				}
			}
			print("\n");
		}
	}
	// Coverted circular Linked list
	public	function makeCircular()
	{
		if ($this->head == NULL)
		{
			echo "Empty Linked List", "\n";
		}
		else
		{
			$temp = $this->head;
			// Find last node
			while ($temp->next != NULL)
			{
				$temp = $temp->next;
				if ($temp == $this->head)
				{
					// Already circular Linked list
					return;
				}
			}
			// Connect last node to first node
			$temp->next = $this->head;
		}
	}
	public static
	function main($args)
	{
		$ll = new LinkedList();
		// Insert element of linked list
		$ll->head = new LinkNode(1);
		$ll->head->next = new LinkNode(2);
		$ll->head->next->next = new LinkNode(3);
		$ll->head->next->next->next = new LinkNode(4);
		$ll->head->next->next->next->next = new LinkNode(5);
		$ll->head->next->next->next->next->next = new LinkNode(6);
		$ll->head->next->next->next->next->next->next = new LinkNode(7);
		$ll->display();
		if ($ll->isCircular())
		{
			echo "Circular Yes", "\n";
		}
		else
		{
			echo "Circular No", "\n";
		}
		echo "After Convert", "\n";
		$ll->makeCircular();
		if ($ll->isCircular())
		{
			echo "Circular Yes", "\n";
		}
		else
		{
			echo "Circular No", "\n";
		}
	}
}
LinkedList::main(array());

Output

Linked List Element :  1  2  3  4  5  6  7
Circular No
After Convert
Circular Yes