Does PHP have built-in data structures?

Solution 1:

The only native data structure in PHP is array. Fortunately, arrays are quite flexible and can be used as hash tables as well.

http://www.php.net/array

However, there is SPL which is sort of a clone of C++ STL.

http://www.php.net/manual/en/book.spl.php

Solution 2:

PHP offers data structures through the Standard PHP Library (SPL) basic extension, which is available and compiled by default in PHP 5.0.0.

The data structures offered are available with PHP 5 >= 5.3.0, and includes:

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 class
  • SplStack class
  • SplQueue class

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 class
  • SplMaxHeap class
  • SplMinHeap class
• SplPriorityQueue class

Arrays

Arrays are structures that store the data in a continuous way, accessible via indexes. Don’t confuse them with PHP arrays: PHP arrays are in fact implemented as ordered hashtables.

• SplFixedArray class

Map

A map is a datastructure holding key-value pairs. PHP arrays can be seen as maps from integers/strings to values. SPL provides a map from objects to data. This map can also be used as an object set.

• SplObjectStorage class

Source: http://php.net/manual/en/spl.datastructures.php

Solution 3:

PHP 7 introduced an extension called ds providing specialized data structures as an alternative to the array.

The ds,

• uses the Ds\ namespace.
• has 3 interfaces namely,Collection, Sequence and Hashable
• has 8 classes namely, Vector, Deque,Queue, PriorityQueue, Map, Set, Stack, and Pair

For more information checkout the Manual and also This blog post has some awesome information including benchmarks.

Solution 4:

The associative array can be used for most basic data structures hashtable, queue, stack. But if you want something like a tree or heap I don't think they exist by default but I'm sure there are free libraries anywhere.

To have an array emulate a stack use array_push() to add and array_pop() to take off

To have an array emulate a queue use array_push() to enqueue and array_shift() to dequeue

An associative array is a hash by default. In PHP they are allowed to have strings as indexes so this works as expected:

$array['key'] = 'value';

Finally, you can kind of emulate a binary tree with an array with the potential to have wasted space. Its useful if you know you're going to have a small tree. Using a linear array, you say for any index (i) you put its left child at index (2i+1) and right child at index (2i+2).

All of these methods are covered nicely in this article on how to make JavaScript arrays emulate higher level data structures.