(PHP 5 >= 5.1.0, PHP 7) Check whether the current element is valid

(PHP 5 >= 5.1.0, PHP 7) Check whether the current element of the iterator is acceptable

(PHP 5 >= 5.1.0, PHP 7) Move the iterator forward

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

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

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

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

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