(PHP 5 >= 5.3.0, PHP 7) Peeks at the node from the end of the doubly linked list

(PHP 5 >= 5.4.0, PHP 7) Unserializes the storage

(PHP 5 >= 5.3.0, PHP 7) Return current node index

(PHP 5 >= 5.3.0, PHP 7) Returns the mode of iteration

(PHP 5 >= 5.3.0, PHP 7) Sets the mode of iteration

(PHP 5 >= 5.3.0, PHP 7) Sets the value at the specified $index to $newval

(PHP 5 >= 5.5.0, PHP 7) Add/insert a new value at the specified index

(PHP 5 >= 5.3.0, PHP 7) Rewind iterator back to the start

(PHP 5 >= 5.3.0, PHP 7) Check whether the doubly linked list contains more nodes

(PHP 5 >= 5.3.0, PHP 7) Checks whether the doubly linked list is empty.