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

Removes and returns the root element according to heap comparison order.

The examples focus on the operation itself, including the important distinction: top returns the same root without removal.

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::extract()

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

SplMaxHeap is used because the abstract SplHeap cannot be instantiated. The extract call is shown on a small, inspectable dataset.

<?php
$heap = new SplMaxHeap();
$heap->insert(4);
$heap->insert(12);
$heap->insert(7);
echo json_encode($heap->extract());
echo " remaining=" . count($heap);

Output from a successful local PHP 8.4 run:

12 remaining=2

Example 2: Checking Behavior

SplMaxHeap is used because the abstract SplHeap cannot be instantiated. The extract call is shown on a small, inspectable dataset.

<?php
$heap = new SplMaxHeap();
$heap->insert(2);
$heap->insert(9);
$heap->insert(5);
$heap->insert(1);
echo json_encode($heap->extract());
echo " remaining=" . count($heap);

Output from a successful local PHP 8.4 run:

9 remaining=3

Example 3: Practical Example

SplMaxHeap is used because the abstract SplHeap cannot be instantiated. The extract call is shown on a small, inspectable dataset.

<?php
$heap = new SplMaxHeap();
$heap->insert(19);
$heap->insert(3);
$heap->insert(11);
echo json_encode($heap->extract());
echo " remaining=" . count($heap);

Output from a successful local PHP 8.4 run:

19 remaining=2

Important Behavior and Edge Cases

An empty heap raises RuntimeException; extraction mutates the heap.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• Removes and returns the root element according to heap comparison order.
• An empty heap raises RuntimeException; extraction mutates the heap.
• top returns the same root without removal.

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