(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) Get the inner iterator

(PHP 5 >= 5.1.0, PHP 7) Checks if the iterator is valid