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

Tests whether the priority queue currently has zero entries.

The examples focus on the operation itself, including the important distinction: valid checks whether there are entries left for traversal.

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

SplPriorityQueue::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 queue is a max-priority queue; equal priorities have no guaranteed FIFO order. The isEmpty call is shown on a small, inspectable dataset.

<?php
$heap = new SplPriorityQueue();
$heap->insert('task-4', 4);
$heap->insert('task-12', 12);
$heap->insert('task-7', 7);
echo $heap->isEmpty() ? "empty" : "not empty";

Output from a successful local PHP 8.4 run:

not empty

Example 2: Checking Behavior

The queue is a max-priority queue; equal priorities have no guaranteed FIFO order. The isEmpty call is shown on a small, inspectable dataset.

<?php
$heap = new SplPriorityQueue();
$heap->insert('task-2', 2);
$heap->insert('task-9', 9);
$heap->insert('task-5', 5);
$heap->insert('task-1', 1);
echo $heap->isEmpty() ? "empty" : "not empty";

Output from a successful local PHP 8.4 run:

not empty

Example 3: Practical Example

The queue is a max-priority queue; equal priorities have no guaranteed FIFO order. The isEmpty call is shown on a small, inspectable dataset.

<?php
$heap = new SplPriorityQueue();
$heap->insert('task-19', 19);
$heap->insert('task-3', 3);
$heap->insert('task-11', 11);
echo $heap->isEmpty() ? "empty" : "not empty";

Output from a successful local PHP 8.4 run:

not empty

Important Behavior and Edge Cases

extract and iterator next remove entries, unlike normal array iteration.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• Tests whether the priority queue currently has zero entries.
• extract and iterator next remove entries, unlike normal array iteration.
• valid checks whether there are entries left for traversal.

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