# PHP - Insert a new node at the end of the Circular Doubly Linked List

In this method, a new node is inserted at the end of the circular doubly linked list. For example - if the given List is 10->20->30 and a new element 100 is added at the end, the List becomes 10->20->30->100.

Inserting a new node at the end of the circular doubly linked list is very easy. First, a new node with given element is created. It is then added at the end of the list by linking the last node and head node to the new node.

The function *push_back* is created for this purpose. It is a **6-step process**.

public function push_back($newElement) { //1. allocate node $newNode = new Node(); //2. assign data element $newNode->data = $newElement; //3. assign null to the next and prev // of the new node $newNode->next = null; $newNode->prev = null; //4. Check the list is empty or not, // if empty make the new node as head if($this->head == null) { $this->head = $newNode; $newNode->next = $this->head; $newNode->prev = $this->head; } else { //5. Else, traverse to the last node $temp = new Node(); $temp = $this->head; while($temp->next !== $this->head) { $temp = $temp->next; } //6. Adjust the links $temp->next = $newNode; $newNode->next = $this->head; $newNode->prev = $temp; $this->head->prev = $newNode; } }

The below is a complete program that uses above discussed concept to insert new node at the end of the circular doubly linked list.

<?php //node structure class Node { public $data; public $next; public $prev; } class LinkedList { public $head; public function __construct(){ $this->head = null; } //Add new element at the end of the list public function push_back($newElement) { $newNode = new Node(); $newNode->data = $newElement; $newNode->next = null; $newNode->prev = null; if($this->head == null) { $this->head = $newNode; $newNode->next = $this->head; } else { $temp = new Node(); $temp = $this->head; while($temp->next !== $this->head) { $temp = $temp->next; } $temp->next = $newNode; $newNode->next = $this->head; $newNode->prev = $temp; $this->head->prev = $newNode; } } //display the content of the list public function PrintList() { $temp = new Node(); $temp = $this->head; if($temp != null) { echo "\nThe list contains: "; while(true) { echo $temp->data." "; $temp = $temp->next; if($temp == $this->head) break; } } else { echo "\nThe list is empty."; } } }; // test the code $MyList = new LinkedList(); //Add three elements at the end of the list. $MyList->push_back(10); $MyList->push_back(20); $MyList->push_back(30); $MyList->PrintList(); ?>

The above code will give the following output:

The list contains: 10 20 30