gistfile1.php

<?php
/**
 * @author Evgeny Shpilevsky <evgeny@shpilevsky.com>
 */

class MyArrayIterator implements Iterator
{

    /**
     * @var array
     */
    protected $array = array();

    /**
     * @param array $array
     */
    public function __construct(array $array)
    {
        $this->array = $array;
    }


    /**
     * Return the current element
     * @link http://php.net/manual/en/iterator.current.php
     * @return mixed Can return any type.
     */
    public function current()
    {
        return current($this->array);
    }

    /**
     * Move forward to next element
     * @link http://php.net/manual/en/iterator.next.php
     * @return void Any returned value is ignored.
     */
    public function next()
    {
        next($this->array);
    }

    /**
     * Return the key of the current element
     * @link http://php.net/manual/en/iterator.key.php
     * @return mixed scalar on success, or null on failure.
     */
    public function key()
    {
        return key($this->array);
    }

    /**
     * Checks if current position is valid
     * @link http://php.net/manual/en/iterator.valid.php
     * @return boolean The return value will be casted to boolean and then evaluated.
     * Returns true on success or false on failure.
     */
    public function valid()
    {
        return isset($this->array[$this->key()]);
    }

    /**
     * Rewind the Iterator to the first element
     * @link http://php.net/manual/en/iterator.rewind.php
     * @return void Any returned value is ignored.
     */
    public function rewind()
    {
        reset($this->array);
    }

}

class MyIteratorAggregate implements IteratorAggregate
{
    /**
     * Retrieve an external iterator
     * @link http://php.net/manual/en/iteratoraggregate.getiterator.php
     * @return Traversable An instance of an object implementing <b>Iterator</b> or <b>Traversable</b>
     */
    public function getIterator()
    {
        return new ArrayIterator([1, 2, 3, 4]);
    }

}

// Example
$iterator = new MyArrayIterator([1, 2, 3, 5]);

// output array
var_dump(iterator_to_array($iterator));

// output all values of array
foreach ($iterator as $value) {
    var_dump($value);
}

// aggregate
$iteratorAggregate = new MyIteratorAggregate();
foreach($iteratorAggregate as $value) {
    var_dump($value);
}