There finally is documentation for SplDoublyLinkedList, SplStack and SplQueue and some "new" classes: SplHeap (abstract), SplMaxHeap, SplMinHeap and SplPriorityQueue, documentation of those classes is in progress.

An example of the new functionality (for SplPriorityQueue) is included in the post showing the insertion of a value into a pre-existing array (without having to slice or splice!).