Building a circular linked list is not at as hard as it sounds from the name. So far, we have seen that adding a new node at the end is pretty simple; we set the next reference of the last node to NULL. In a circular linked list, the last node's next reference will actually point to the first node, thereby creating a circular list. Let's write a simple circular linked list where the nodes will be inserted at the end of the list:
class CircularLinkedList {
private $_firstNode = NULL;
private $_totalNode = 0;
public function insertAtEnd(string $data = NULL) {
$newNode = new ListNode($data);
if ($this->_firstNode === NULL) {
$this->_firstNode = &$newNode;
} else {
$currentNode = $this->_firstNode;
while ($currentNode->next !== $this->_firstNode) {
...
