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PHP | SplDoublyLinkedList unshift() Function
  • Last Updated : 23 Aug, 2019
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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("GeeksforGeeks");
  
// Display the list elements
print_r($list);
  
?> 
Output:
SplDoublyLinkedList Object
(
    [flags:SplDoublyLinkedList:private] => 0
    [dllist:SplDoublyLinkedList:private] => Array
        (
            [0] => GeeksforGeeks
            [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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