(PHP 5 >= 5.1.0, PHP 7) Forward to the next element

(PHP 5 >= 5.1.0, PHP 7) Prevents the rewind operation on the inner iterator.

(PHP 5 >= 5.1.0, PHP 7) Validates the iterator

(PHP 5 >= 5.1.0, PHP 7) Construct a NoRewindIterator

(PHP 5 >= 5.1.0, PHP 7) Get the current value

(PHP 5 >= 5.1.0, PHP 7) Get the inner iterator

(PHP 5 >= 5.1.0, PHP 7) Get the current key