Iterates over all combinations of the values on an input array

CombinatorialIterator.php

<?php

class CombinatorialIterator implements \Iterator
{
    protected $valid;
    protected $iteration;
    protected $data;

    public function __construct(array $data = array())
    {
        $this->data = $data;
    }

    public function current()
    {
        $result = array();
        foreach ($this->data as $name => $value) {
            $result[$name] = is_array($value) ? current($value) : $value;
        }

        return $result;
    }

    public function next()
    {
        $this->valid = false;
        foreach ($this->data as $name => $value) {
            if (is_array($value)) {
                next($this->data[$name]);
                if (key($this->data[$name]) !== null) {
                    $this->valid = true;
                    break;
                }
                reset($this->data[$name]);
            }
        }
        ++$this->iteration;
    }

    public function key()
    {
        return $this->iteration;
    }

    public function valid()
    {
        return $this->valid;
    }

    public function rewind()
    {
        $this->valid = !empty($this->data);
        $this->iteration = 0;
        foreach ($this->data as $name => $value) {
            if (is_array($value)) {
                reset($this->data[$name]);
            }
        }
    }
}

CombinatorialIteratorTest.php

<?php

class CombinatorialIteratorTest extends \PHPUnit_Framework_TestCase
{
    public function testEmptyConstruction()
    {
        $iterator = new CombinatorialIterator();

        $this->assertNotNull($iterator);
    }

    /**
     * @dataProvider providerValidInput
     */
    public function testValidInput($input, $expected)
    {
        $this->assertEquals($expected, iterator_to_array(new CombinatorialIterator($input)));
    }

    public function providerValidInput()
    {
        return array(
            'default' => array(
                array(),
                array(),
            ),
            'single scalar' => array(
                array('scalar' => 'value'),
                array(
                    array('scalar' => 'value'),
                ),
            ),
            'multiple scalar' => array(
                array('scalar1' => 'value1', 'scalar2' => 'value2'),
                array(
                    array('scalar1' => 'value1', 'scalar2' => 'value2'),
                ),
            ),
            'single array' => array(
                array('option' => array('first', 'second')),
                array(
                    array('option' => 'first'),
                    array('option' => 'second'),
                ),
            ),
            'multiple array' => array(
                array(
                    'name' => array('Bob', 'John'),
                    'surname' => array('Spongebob', 'Snow'),
                ),
                array(
                    array('name' => 'Bob',  'surname' => 'Spongebob', ),
                    array('name' => 'John', 'surname' => 'Spongebob', ),
                    array('name' => 'Bob',  'surname' => 'Snow', ),
                    array('name' => 'John', 'surname' => 'Snow', ),
                ),
            ),
            'mixed' => array(
                array(array('A', 'B'), 'C', array('D', 'E', 'F'), 'G'),
                array(
                    array('A', 'C', 'D', 'G'),
                    array('B', 'C', 'D', 'G'),
                    array('A', 'C', 'E', 'G'),
                    array('B', 'C', 'E', 'G'),
                    array('A', 'C', 'F', 'G'),
                    array('B', 'C', 'F', 'G'),
                ),
            ),
        );
    }
}