Master PHP Data Structures: Stack, Queue, and Min-Heap with SPL

Heap is a data structure designed to implement priority queues, typically built using a binary heap. A heap where the root is the largest is called a max‑heap, while a heap where the root is the smallest is a min‑heap, which is also used for heap sort.

The following diagram illustrates a min‑heap where each node’s priority is not less than that of its children:

PHP’s Standard PHP Library (SPL) provides built‑in implementations of common data structures. While arrays can be used to simulate stacks or queues, they are not specialized and can lead to errors. SPL classes such as SplStack, SplQueue, SplMinHeap, and SplFixedArray offer dedicated, efficient implementations.

Stack implementation

$stack = new SplStack();
// push
$stack->push('a');
$stack->push('b');
// pop
echo $stack->pop();
echo $stack->pop();

Queue implementation

$queue = new SplQueue();
// enqueue
$queue->enqueue('a');
$queue->enqueue('b');
$queue->enqueue('c');
// dequeue
echo $queue->dequeue();
echo $queue->dequeue();
echo $queue->dequeue();

Min‑heap implementation

$heap = new SplMinHeap();
// insert
$heap->insert('a');
$heap->insert('b');
// extract
echo $heap->extract();
echo $heap->extract();

Fixed‑length array

$array = new SplFixedArray(5);
$array[1] = 5;
var_dump($array);