(PHP 5 >= 5.3.0, PHP 7) Return current node pointed by the iterator

(PHP 5 >= 5.3.0, PHP 7) Constructs a new empty heap

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

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

(PHP 5 >= 5.3.0, PHP 7) Counts the number of elements in the heap.

(PHP 5 >= 5.3.0, PHP 7) Compare elements in order to place them correctly in the heap while sifting up.

(PHP 5 >= 5.3.0, PHP 7) Extracts a node from top of the heap and sift up.

(PHP 5 >= 5.3.0, PHP 7) Rewind iterator back to the start (no-op)

(PHP 5 >= 5.3.0, PHP 7) Recover from the corrupted state and allow further actions on the heap.

(PHP 5 >= 5.3.0, PHP 7) Checks whether the heap is empty.