ArrayObject implementation

gistfile1.php

<?php

if (!class_exists('ArrayObject')) {
class ArrayObject implements IteratorAggregate, Traversable, ArrayAccess, Serializable, Countable
{
    const STD_PROP_LIST = 1;
    const ARRAY_AS_PROPS = 2;

    protected $_array = array();
    protected $_flags = 0;
    protected $_iterator_class = 'ArrayIterator';

    public function __construct ($input = array(), $flags = 0, $iterator_class = 'ArrayIterator')
    {
        $this->_array = (array)$input;
        $this->_flags = $flags;
        if ($iterator_class)
            $this->_iterator_class = $iterator_class;
    }
    
    public function __set($name, $value)
    {
        $this->_array[$name] = $value;
    }

    public function __get($name)
    {
        if (array_key_exists($name, $this->_array)) {
            return $this->_array[$name];
        }
        return null;
    }

    public function __isset($name)
    {
        return isset($this->_array[$name]);
    }

    public function __unset($name)
    {
        unset($this->_array[$name]);
    }

    public function append($value)
    {
        array_push($this->_array, $value);
    }

    public function asort()
    {
        asort($this->_array);
    }

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

    public function exchangeArray($input)
    {
        $this->_array = (array)$input;
    }

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

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

    public function getIterator()
    {
        $cls = $this->_iterator_class;
        return new $cls($this->_array);
    }

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

    public function ksort()
    {
        ksort($this->_array);
    }

    public function natcasesort()
    {
        natcasesort($this->_array);
    }

    public function natsort()
    {
        natsort($this->_array);
    }

    public function offsetExists($index)
    {
        return array_key_exists($index, $this->_array);
    }

    public function offsetGet($index)
    {
        return $this->_array[$index];
    }

    public function offsetSet($index, $newval)
    {
        if(null === $index)
            $this->_array[] = $newval;
        else
            $this->_array[$index] = $newval;
    }

    public function offsetUnset($index)
    {
        unset($this->_array[$index]);
    }

    public function serialize()
    {
        return serialize($this);
    }

    public function setFlags($flags)
    {
        $this->_flags = $flags;
    }

    public function setIteratorClass($iterator_class)
    {
        $this->_iterator_class = $iterator_class;
    }

    public function uasort($cmp_function)
    {
        uasort($this->_array, $cmp_function);
    }

    public function uksort($cmp_function)
    {
        uksort($this->_array, $cmp_function);
    }

    public function unserialize($serialized)
    {
        $tmp = unserialize($serialized);
        $this->_array = $tmp->_array;
        $this->_flags = $tmp->_flags;
        $this->_iterator_class = $tmp->_iterator_class;
    }
}
}