index.php

<?PHP
class Node {
    public $data;
    public $next;
    public $br = '<br>';

    public function __construct($data, $next = null){
        $this->data = $data;
        $this->next = $next;
    }
}

class LinkedList {
    public $head;
    public $size;

    public function __construct(){
        $this->head = null;
        $this->size = 0;
    }

    public function insertFirst($data){
        $this->head = new Node($data, $this->head);
        $this->size++;
    }

    public function insertAt($data, $index){
        if($index > 0 && $index > $this->size){
            return ;
        }
        if($index === 0 ){
            $this->insertFirst($data);
        }
        $node = new Node($data);
        $current;
        $previous;

        $current = $this->head;
        $count  = 0;
        while ($count < $index) {
            $previous = $current;
            $count++;
            $current = $current->next;
        }

        $node->next = $current;
        $previous->next = $node;

        $this->size++;
    }

    public function removeAt($index){
        if($index > 0  && $index > $this->size ){
            return;
        }
        $current = $this->head;
        $previous;
        $count = 0;
        if($index === 0){
            $this->head = $current->next;
        }else{         
        while($count < $index){
                $count++;
                $previous = $current;
                $current = $current->next;
            }
            $previous->next = $current->next;
        }
        $this->size--;
    }

    public function insertLast($data){
        $node = new Node($data);
       // $current;
        if(!$this->head){
            $this->head = $node;
        }else{
            $current = $this->head;
            while ($current->next) {
                $current = $current->next;
            }
          $current->next = $node;
        }
          $this->size++;
    }
    public function getAt($index){
        $current = $this->head;
        $count = 0;

        while ($current) {
            if($count == $index){
                print_r($current->data);
            }
            $count++;
            $current = $current->next;
        }
        return null;
    }
    public function clearList(){
        $this->head = null;
        $this->size = 0;
    }

    public function printListData(){
        $current = $this->head;
        while($current){
            echo  $current->data;
            $current = $current->next;
        }
    }
}
$ll = new LinkedList();
$ll->insertFirst();
$ll->insertFirst();
$ll->insertFirst();
$ll->insertLast();
$ll->insertAt();
$ll->getAt();
$ll->removeAt();
$ll->clearList();
$ll->printListData();