PHP overloaded array operator_PHP tutorial

class BtstoreRoot

{

    /**

     * 根结点

     * @var BtstoreElement

     */

    static $root;

}

class BtstoreElement implements ArrayAccess, Iterator

{

    /**

     * 当前所代表的目录

     * @var string

     */

    private $dataDir;

    /**

     * 当前所代表的数据

     * @var array

     */

    private $arrData;

    /**

     * 构造函数

     * @param string $dataDir

     * @param array $arrData

     */

    function __construct($dataDir, $arrData)

    {

        $this->dataDir = '';

        $this->arrData = array ();

        if (! empty ( $dataDir ) && is_dir ( $dataDir ))

        {

            $this->dataDir = $dataDir;

        }

        if (! empty ( $arrData ))

        {

            $this->arrData = $arrData;

        }

    }

    function __get($key)

    {

        if (isset ( $this->arrData [$key] ))

        {

            $data = $this->arrData [$key];

            if (is_array ( $data ) && ! is_object ( $data ))

            {

                $data = new BtstoreElement ( '', $data );

            }

            return $data;

        }

        if (! empty ( $this->dataDir ))

        {

            $path = $this->dataDir . '/' . $key;

            if (is_dir ( $path ))

            {

                $data = new BtstoreElement ( $path, null );

                $this->arrData [$key] = $data;

                return $data;

            }

            if (is_file ( $path ))

            {

                $content = file_get_contents ( $path );

                $arrData = unserialize ( $content );

                $data = new BtstoreElement ( '', $arrData );

                $this->arrData [$key] = $data;

                return $data;

            }

        }

        trigger_error ( "undefined index:$key" );

    }

    function __isset($key)

    {

        if (isset ( $this->arrData [$key] ))

        {

            return true;

        }

        if (file_exists ( $this->dataDir . '/' . $key ))

        {

            return true;

        }

        return false;

    }

    function toArray()

    {

        return $this->arrData;

    }

    /* (non-PHPdoc)

     * @see ArrayAccess::offsetExists()

     */

    public function offsetExists($offset)

    {

        return $this->__isset ( $offset );

    }

    /* (non-PHPdoc)

     * @see ArrayAccess::offsetGet()

     */

    public function offsetGet($offset)

    {

        return $this->__get ( $offset );

    }

    /* (non-PHPdoc)

     * @see ArrayAccess::offsetSet()

     */

    public function offsetSet($offset, $value)

    {

        trigger_error ( 'offsetSet not implemented by BtstoreElement' );

    }

    /* (non-PHPdoc)

     * @see ArrayAccess::offsetUnset()

     */

    public function offsetUnset($offset)

    {

        trigger_error ( 'offsetUnset not implemented by BtstoreElement' );

    }

    /* (non-PHPdoc)

     * @see Iterator::current()

     */

    public function current()

    {

        return current ( $this->arrData );

    }

    /* (non-PHPdoc)

     * @see Iterator::next()

     */

    public function next()

    {

        return next ( $this->arrData );

    }

    /* (non-PHPdoc)

     * @see Iterator::key()

     */

    public function key()

    {

        return key ( $this->arrData );

    }

    /* (non-PHPdoc)

     * @see Iterator::valid()

     */

    public function valid()

    {

        $data = current ( $this->arrData );

        return ! empty ( $data );

    }

    /* (non-PHPdoc)

     * @see Iterator::rewind()

     */

    public function rewind()

    {

        reset ( $this->arrData );

    }

}

/**

 * 获取一个BtstoreElement对象

 * @return BtstoreElement

 */

function btstore_get()

{

    if (empty ( BtstoreRoot::$root ))

    {

        BtstoreRoot::$root = new BtstoreElement ( ScriptConf::BTSTORE_ROOT, null );

    }

    return BtstoreRoot::$root;

}