The contents are included as follows: Array, Linked List, Stack and Queue, Recursion, Tree and Forest, Graph, Sorting, Indexing and Hashing Structure, etc.

Stacks and Queues are often considered the bread and butter of data structures and find use in architecture, parsing, operating systems, and discrete event simulation.

The new additions to SPL add some useful functionality to PHP that is easy to use, as well as implementations of data structures, such as doubly linked lists, stacks, heaps, and queues.