(PHP 5 >= 5.4.0, PHP 7) Calculate a unique identifier for the contained objects

(PHP 5 >= 5.3.0, PHP 7) Peeks at the node from the top of the queue

(PHP 5 >= 5.1.0, PHP 7) Gets line from file

(PHP 5 >= 5.1.2, PHP 7) Unregister given function as __autoload() implementation

(PHP 5 >= 5.3.0, PHP 7) Check whether the queue contains more nodes

(PHP 5, PHP 7) Get the current depth of the recursive iteration

(PHP 5 >= 5.2.2, PHP 7) Serializes the storage

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

(PHP 5 >= 5.1.0, PHP 7) Portable file locking

(PHP 5 >= 5.1.2, PHP 7) Register given function as __autoload() implementation