Predefined Constants
SplDoublyLinkedList
SPL
PHP Manual

# Datastructures

## Table of Contents

- The SplDoublyLinkedList class
- The SplStack class
- The SplQueue class
- The SplHeap class
- The SplMaxHeap class
- The SplMinHeap class
- The SplPriorityQueue class

SPL provides a set of standard datastructures. They are grouped here by their underlying implementation which usually defines their general field of application.

## Doubly Linked Lists

A Doubly Linked List (DLL) is a list of nodes linked in both directions to each others. Iterator's operations, access to both ends, addition or removal of nodes have a cost of O(1) when the underlying structure is a DLL. It hence provides a decent implementation for stacks and queues.

- SplDoublyLinkedList
  - SplStack
  - SplQueue

## Heaps

Heaps are tree-like structures that follow the heap-property: each node is greater than or equal to its children, when compared using the implemented compare method which is global to the heap.

- SplHeap
  - SplMaxHeap
  - SplMinHeap
- SplPriorityQueue

Predefined Constants
SplDoublyLinkedList
SPL
PHP Manual