PHP overloaded array operator_PHP tutorial

PHP provides many interfaces to implement some very specific functions. For example, if you want to use an object as an array, you only need to implement the ArrayAccess interface. When you want to use an object in foreach When , you only need to implement the Iterator interface. Here is an example

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;
}