Continuing on his his series looking at improvements in the upcoming PHP 5.3 release, Johannes Schluter uses this new post to look at some of the new data structures their update will have to offers in the Standard PHP Library.

In the programming world there are quite a few well understood and explored data structures. Which are commonly used in tons of applications, still the only things PHP offered till 5.3 in regards to structuring data were arrays (more precise: hash tables) and objects. So people had to either abuse them for other structures or implement the structures themselves on top of these. Thanks to Etienne things now are changing and PHP's Standard PHP Library (SPL) extension will offer quite a few standard implementations of data structures.

These new data structures are SplDoublyLinkedList, SplStack, SplQueue/SplPirorityQueue, SplHeap/SplMinHeap/SplMaxHeap and SplFixedArray. He explains a bit of what they are and more detail on one specifically - SplFixedArray.

On his blog, Dan Scott notes that the PHP language will be getting a native doubly-linked list structure in the coming days (as mentioned by Etienne Kneuss).

This is fabulous news; when I wrote the File_MARC PEAR package, I ended up having to implement a linked list class in PEAR to support it.

Doubly linked lists are normal lists, but the elements also have links to both the previous and next items in the list as well. Two other structures will be added right along with it - SplStack and SplQueue.