PHP SplDoublyLinkedList key() Function

The SplDoublyLinkedList::key() function is an inbuilt function in PHP which is used to return the index of the current node. Syntax:

mixed SplDoublyLinkedList::key( void )

Parameters: This function does not accepts any parameters. Return Value: It returns the index of current node. Below programs illustrate the SplDoublyLinkedList::key() function in PHP: Program 1:

php

<?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::key() function
// to get the key
var_dump($list->key());

// Use next() function to increment
// the index value
$list->next();

// Use SplDoublyLinkedList::key() function
// to get the key
var_dump($list->key());

?>

Output:

int(0)
int(1)

Program 2:

php

<?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);

$list->rewind();

// Use SplDoublyLinkedList::key() function
// to get the key
var_dump($list->key());

// Use next() function to increment
// the index value
$list->next();
$list->next();
$list->next();

// Use SplDoublyLinkedList::key() function
// to get the key
var_dump($list->key());

?>

Output:

int(0)
int(3)

Reference: https://www.php.net/manual/en/spldoublylinkedlist.key.php

PHP SplDoublyLinkedList key() Function

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