(PHP 5 >= 5.1.0, PHP 7) Forward to the next element
(PHP 5 >= 5.1.0, PHP 7) Get the current value
(PHP 5 >= 5.1.0, PHP 7) Get the key of the current element
(PHP 5 >= 5.1.0, PHP 7) Rewind to the first element
(PHP 5 >= 5.1.0, PHP 7) Create an iterator from anything that is traversable
(PHP 5 >= 5.1.0, PHP 7) Checks if the iterator is valid
(PHP 5 >= 5.1.0, PHP 7) Get the inner iterator