PHP SplQueue::dequeue() Method: Usage and Examples

Removes and returns the oldest item in a first-in-first-out queue.

The examples focus on the operation itself, including the important distinction: enqueue appends a new item; dequeue removes the oldest.

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

SplQueue::dequeue()

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

enqueue appends; dequeue returns and removes the oldest queued value. SplQueue is a FIFO specialization of SplDoublyLinkedList.

<?php
$queue = new SplQueue();
$queue->enqueue('red');
$queue->enqueue('blue');
echo json_encode($queue->dequeue());
echo json_encode(iterator_to_array($queue));

Output from a successful local PHP 8.4 run:

"red"["blue"]

Example 2: Checking Behavior

enqueue appends; dequeue returns and removes the oldest queued value. SplQueue is a FIFO specialization of SplDoublyLinkedList.

<?php
$queue = new SplQueue();
$queue->enqueue('one');
$queue->enqueue('two');
echo json_encode($queue->dequeue());
echo json_encode(iterator_to_array($queue));

Output from a successful local PHP 8.4 run:

"one"["two"]

Example 3: Practical Example

enqueue appends; dequeue returns and removes the oldest queued value. SplQueue is a FIFO specialization of SplDoublyLinkedList.

<?php
$queue = new SplQueue();
$queue->enqueue(3);
$queue->enqueue(7);
echo json_encode($queue->dequeue());
echo json_encode(iterator_to_array($queue));

Output from a successful local PHP 8.4 run:

3[7]

Important Behavior and Edge Cases

An empty queue raises RuntimeException; always verify it has entries before dequeuing.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• Removes and returns the oldest item in a first-in-first-out queue.
• An empty queue raises RuntimeException; always verify it has entries before dequeuing.
• enqueue appends a new item; dequeue removes the oldest.

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