PHP iterable interfaces

Iterator.php

<?php

interface Iterator extends Traversable 
{
  abstract public mixed current ( void )
  abstract public scalar key ( void )
  abstract public void next ( void )
  abstract public void rewind ( void )
  abstract public boolean valid ( void )
}

IteratorAggregate.php

<?php

interface IteratorAggregate extends Traversable 
{
  abstract public Traversable getIterator( void )
}

Traversable.php

<?php

/**
 * Interface to detect if a class is traversable using foreach.
 * Abstract base interface that cannot be implemented alone. Instead it must be implemented by either IteratorAggregate or Iterator.
 */
abstract interface Traversable
{}