PHP Manual Function Reference Other Basic Extensions SPL Datastructures SplDoublyLinkedList SplDoublyLinkedList::key SplDoublyLinkedList::isEmpty SplDoublyLinkedList::next SplDoublyLinkedList::key (PHP 5 >= 5.3.0)SplDoublyLinkedList::key — Return current node index Description public mixed SplDoublyLinkedList::key ( void ) This function returns the current node index Parameters This function has no parameters. Return Values The current node index.