PHP SplDoublyLinkedList offsetExists() Function

<?php 

// Declare an empty SplDoublyLinkedList
$list = new \SplDoublyLinkedList;

// Use SplDoublyLinkedList::add() function to 
// add elements to the SplDoublyLinkedList
$list->add(0, 30);
$list->add(1, 20);
$list->add(2, 30);
$list->add(3, "Geeks");
$list->add(4, 'G');
$list->rewind();

// Use SplDoublyLinkedList::offsetExists() function
// to check index exist or not
var_dump($list->offsetExists(2));

var_dump($list->offsetExists(10));

?> 

<?php 

// Declare an empty SplDoublyLinkedList
$list = new \SplDoublyLinkedList();

// Use SplDoublyLinkedList::push() function to 
// add elements to the SplDoublyLinkedList
$list->push(1);
$list->push(2);
$list->push(3);
$list->push(8);
$list->push(5);

// Use SplDoublyLinkedList::offsetExists() function
// to check index exist or not
var_dump($list->offsetExists(3));

var_dump($list->offsetExists(15));

?>