PHP SplDoublyLinkedList::offsetSet() Method: Usage and Examples

Assigns a value at a numeric offset or appends when the offset is null.

The examples focus on the operation itself, including the important distinction: add inserts and shifts elements, while offsetSet replaces or appends.

What It Does

Use the examples below to observe the behavior on a small dataset before extending it to application code.

Syntax and Return Value

SplDoublyLinkedList::offsetSet($index, mixed $value)

The displayed signature describes the API or identifies any correction or optional dependency. When a parameter is optional, supply it only when the task requires it.

Parameters

• index: required.
• value: required.

Example 1: Basic Use

The list begins with 3 values. Notice how offsetSet changes or observes its indexed deque rather than an ordinary associative array.

<?php
$list = new SplDoublyLinkedList();
$list->push('tea');
$list->push('coffee');
$list->push('water');
$list->offsetSet(1, 'chai');
echo json_encode(iterator_to_array($list));

Output from a successful local PHP 8.4 run:

["tea","chai","water"]

Example 2: Checking Behavior

The list begins with 4 values. Notice how offsetSet changes or observes its indexed deque rather than an ordinary associative array.

<?php
$list = new SplDoublyLinkedList();
$list->push('one');
$list->push('two');
$list->push('three');
$list->push('four');
$list->offsetSet(1, 'replaced');
echo json_encode(iterator_to_array($list));

Output from a successful local PHP 8.4 run:

["one","replaced","three","four"]

Example 3: Practical Example

The list begins with 3 values. Notice how offsetSet changes or observes its indexed deque rather than an ordinary associative array.

<?php
$list = new SplDoublyLinkedList();
$list->push(4);
$list->push(8);
$list->push(12);
$list->offsetSet(2, 9);
echo json_encode(iterator_to_array($list));

Output from a successful local PHP 8.4 run:

[4,8,9]

Important Behavior and Edge Cases

Only an existing offset can be replaced; null means append.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• Assigns a value at a numeric offset or appends when the offset is null.
• Only an existing offset can be replaced; null means append.
• add inserts and shifts elements, while offsetSet replaces or appends.

Use SplDoublyLinkedList::offsetSet when its documented behavior matches the problem. Test the relevant edge cases in your own runtime before deploying it.