Example usage for ArrayAccess interface

Product.php

<?php

class Product implements ArrayAccess
{
    protected $_productId;
    protected $_title;
    protected $_price;
    protected $_arrayAccess;
    
    public function __construct($data = null)
    {
        if (null !== $data) {
            $this->populate($data);
        }
        $this->_arrayAccess = $this->toArray();
    }
    public function setProductId($productId)
    {
        $this->_productId = (int) $productId;
        return $this;
    }
    public function getProductId()
    {
        return $this->_productId;
    }
    public function setTitle($title)
    {
        $this->_title = (string) $title;
        return $this;
    }
    public function getTitle()
    {
        return $this->_title;
    }
    public function setPrice($price)
    {
        $this->_price = (float) $price;
        return $this;
    }
    public function getPrice()
    {
        return $this->_price;
    }
    public function populate($row)
    {
        if (is_array($row)) {
            $row = new ArrayObject($row, ArrayObject::ARRAY_AS_PROPS);
        }
        $this->setProductId($row->productId)
            ->setTitle($row->title)
            ->setPrice($row->price);
    }
    public function toArray()
    {
        return array (
            'productId' => $this->getProductId(),
            'title' => $this->getTitle(),
            'price' => $this->getPrice(),
        );
    }

    /**
     * (PHP 5 &gt;= 5.0.0)<br/>
     * Whether a offset exists
     * @link http://php.net/manual/en/arrayaccess.offsetexists.php
     * @param mixed $offset <p>
     * An offset to check for.
     * </p>
     * @return boolean true on success or false on failure.
     * </p>
     * <p>
     * The return value will be casted to boolean if non-boolean was returned.
     */
    public function offsetExists($offset)
    {
        return isset ($this->_arrayAccess[$offset]);
    }

    /**
     * (PHP 5 &gt;= 5.0.0)<br/>
     * Offset to retrieve
     * @link http://php.net/manual/en/arrayaccess.offsetget.php
     * @param mixed $offset <p>
     * The offset to retrieve.
     * </p>
     * @return mixed Can return all value types.
     */
    public function offsetGet($offset)
    {
        return $this->offsetExists($offset) ? $this->_arrayAccess[$offset] : null;
    }

    /**
     * (PHP 5 &gt;= 5.0.0)<br/>
     * Offset to set
     * @link http://php.net/manual/en/arrayaccess.offsetset.php
     * @param mixed $offset <p>
     * The offset to assign the value to.
     * </p>
     * @param mixed $value <p>
     * The value to set.
     * </p>
     * @return void
     */
    public function offsetSet($offset, $value)
    {
        if (is_null($offset)) {
            $this->_arrayAccess[] = $value;
        } else {
            $this->_arrayAccess[$offset] = $value;
        }
    }

    /**
     * (PHP 5 &gt;= 5.0.0)<br/>
     * Offset to unset
     * @link http://php.net/manual/en/arrayaccess.offsetunset.php
     * @param mixed $offset <p>
     * The offset to unset.
     * </p>
     * @return void
     */
    public function offsetUnset($offset)
    {
        unset ($this->_arrayAccess[$offset]);
    }

}

ProductCollection.php

<?php

class ProductCollection implements Countable, SeekableIterator
{
    protected $_stack;
    protected $_position;
    protected $_count;
    
    public function __construct()
    {
        $this->rewind();
        $this->_count = 0;
        $this->_stack = array ();
    }
    public function addEntity($entity)
    {
        $this->_stack[] = $entity;
        $this->_count++;
    }
    public function rewind()
    {
        $this->_position = 0;
    }
    public function next()
    {
        $this->_position++;
    }
    public function key()
    {
        return $this->_position;
    }
    public function current()
    {
        return $this->_stack[$this->_position];
    }
    public function valid()
    {
        return isset ($this->_stack[$this->_position]);
    }
    public function seek($position)
    {
        $this->_position = $position;
    }
    public function count()
    {
        return $this->_count;
    }
}

test.php

<?php

require_once 'Product.php';
require_once 'ProductCollection.php';

$productCollection = new ProductCollection();
$productCollection->addEntity(new Product(array ('productId' => 1, 'title' => 'backpack', 'price' => 29.95)));
$productCollection->addEntity(new Product(array ('productId' => 2, 'title' => 'baseball cap', 'price' => 19.95)));
$productCollection->addEntity(new Product(array ('productId' => 3, 'title' => 'tent', 'price' => 195.95)));
$productCollection->addEntity(new Product(array ('productId' => 4, 'title' => 'sleeping bag', 'price' => 69.00)));

echo "We now have {$productCollection->count()} elements in our stack" . PHP_EOL;
foreach ($productCollection as $product) {
    echo $product->getTitle() . "\t" . $product->getPrice() . PHP_EOL;
}
foreach ($productCollection as $product) {
    echo $product['title'] . "\t" . $product['price'] . PHP_EOL;
}

The results are as expected, both OOP as accessed as array:

We now have 4 elements in our stack
backpack 29.95
baseball cap 19.95
tent 195.95
sleeping bag 69
backpack 29.95
baseball cap 19.95
tent 195.95
sleeping bag 69