PHP SplHeap::rewind() Method: Usage and Examples

Implements Iterator::rewind as a no-op on an SPL heap.

The examples focus on the operation itself, including the important distinction: next removes the root, while top peeks without consuming it.

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

SplHeap::rewind()

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

Rewinding does not restore the previously extracted value; it only positions the remaining heap iterator.

<?php
$heap = new SplMaxHeap();
$heap->insert(4);
$heap->insert(12);
$heap->insert(7);
$removed = $heap->extract();
$heap->rewind();
echo json_encode(["removed" => $removed, "current" => $heap->current()]);

Output from a successful local PHP 8.4 run:

{"removed":12,"current":7}

Example 2: Checking Behavior

Rewinding does not restore the previously extracted value; it only positions the remaining heap iterator.

<?php
$heap = new SplMaxHeap();
$heap->insert(2);
$heap->insert(9);
$heap->insert(5);
$heap->insert(1);
$removed = $heap->extract();
$heap->rewind();
echo json_encode(["removed" => $removed, "current" => $heap->current()]);

Output from a successful local PHP 8.4 run:

{"removed":9,"current":5}

Example 3: Practical Example

Rewinding does not restore the previously extracted value; it only positions the remaining heap iterator.

<?php
$heap = new SplMaxHeap();
$heap->insert(19);
$heap->insert(3);
$heap->insert(11);
$removed = $heap->extract();
$heap->rewind();
echo json_encode(["removed" => $removed, "current" => $heap->current()]);

Output from a successful local PHP 8.4 run:

{"removed":19,"current":11}

Important Behavior and Edge Cases

Rewinding cannot restore values consumed by next or extract; the heap is destructive when iterated.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• Implements Iterator::rewind as a no-op on an SPL heap.
• Rewinding cannot restore values consumed by next or extract; the heap is destructive when iterated.
• next removes the root, while top peeks without consuming it.

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