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

Checks whether the list currently contains zero items.

The examples focus on the operation itself, including the important distinction: count returns the number of entries; isEmpty is a direct boolean test.

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::isEmpty()

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.

Example 1: Basic Use

The list begins with 3 values. Notice how isEmpty 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');
echo $list->isEmpty() ? "empty" : "not empty";

Output from a successful local PHP 8.4 run:

not empty

Example 2: Checking Behavior

The list begins with 4 values. Notice how isEmpty 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');
echo $list->isEmpty() ? "empty" : "not empty";

Output from a successful local PHP 8.4 run:

not empty

Example 3: Practical Example

The list begins with 3 values. Notice how isEmpty 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);
echo $list->isEmpty() ? "empty" : "not empty";

Output from a successful local PHP 8.4 run:

not empty

Important Behavior and Edge Cases

An empty list is different from a list containing the value null.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• Checks whether the list currently contains zero items.
• An empty list is different from a list containing the value null.
• count returns the number of entries; isEmpty is a direct boolean test.

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