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