The SplDoublyLinkedList::unshift() function is an inbuilt function in PHP which is used to add the element at the beginning of a doubly linked list.
Syntax:
void SplDoublyLinkedList::unshift( $value )
Parameters: This function accepts a single parameter $value which is used to unshift the value in a doubly linked list.
Return Value: It does not return any value.
Below programs illustrate the SplDoublyLinkedList::unshift() function in PHP:
Program 1:
<?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');   // Use unshift() function $list->unshift("neveropen");   // Display the list elements print_r($list);   ?> |
Output:
SplDoublyLinkedList Object
(
[flags:SplDoublyLinkedList:private] => 0
[dllist:SplDoublyLinkedList:private] => Array
(
[0] => neveropen
[1] => 30
[2] => 20
[3] => 30
[4] => Geeks
[5] => G
)
)
Program 2:
<?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 unshift() function $list->unshift("Geeks");   // Display the list elements print_r($list);   ?> |
Output:
SplDoublyLinkedList Object
(
[flags:SplDoublyLinkedList:private] => 0
[dllist:SplDoublyLinkedList:private] => Array
(
[0] => Geeks
[1] => 1
[2] => 2
[3] => 3
[4] => 8
[5] => 5
)
)
Reference: https://www.php.net/manual/en/spldoublylinkedlist.unshift.php
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