(PHP 5 >= 5.1.0, PHP 7) Move the iterator forward
(PHP 5 >= 5.1.0, PHP 7) Return the inner iterator's children contained in a ParentIterator
(PHP 5 >= 5.1.0, PHP 7) Determines acceptability
(PHP 5 >= 5.1.0, PHP 7) Rewind the iterator
(PHP 5 >= 5.1.0, PHP 7) Constructs a ParentIterator
(PHP 5 >= 5.1.0, PHP 7) Check whether the inner iterator's current element has children