A linked list is a linear data structure, in which the elements are stored in the form of a node. Each node contains two sub-elements. A data part that stores the value of the element and next part that stores the link to the next node as shown in the below image:
The first node also known as HEAD is always used as a reference to traverse the list. The last node points to NULL. Linked list can be visualized as a chain of nodes, where every node points to the next node.
Implementation of Singly Linked List
Representation:
In PHP, singly linked list can be represented as a class and a Node as a separate class. The LinkedList class contains a reference of Node class type.
//node structure
class Node {
public $data;
public $next;
}
class LinkedList {
public $head;
//constructor to create an empty LinkedList
public function __construct(){
$this->head = null;
}
};
Create a Singly Linked List
Let us create a simple singly linked list which contains three data nodes.
Example
<?php
//node structure
class Node {
public $data;
public $next;
}
class LinkedList {
public $head;
//constructor to create an empty LinkedList
public function __construct(){
$this->head = null;
}
};
// test the code
//create an empty LinkedList
$MyList = new LinkedList();
//Add first node.
$first = new Node();
$first->data = 10;
$first->next = null;
//linking with head node
$MyList->head = $first;
//Add second node.
$second = new Node();
$second->data = 20;
$second->next = null;
//linking with first node
$first->next = $second;
//Add third node.
$third = new Node();
$third->data = 30;
$third->next = null;
//linking with second node
$second->next = $third;
?>
