PHP MAP

	class Mapob implements IteratorAggregate,ArrayAccess,Countable
	{
		private $data = array();

		public function add($key,$value)
		{
			$this->data[$key] = $value;
		}

		public function remove($key)
		{
			if(isset($this->data[$key]))
			{
				$value = $this->data[$key];
				unset($this->data[$key]);
				return $value;
			}
			return null;
		}

		public function clean()
		{
			foreach($this->getKeys() as $key)
			{
				$this->remove($key);
			}
		}

		public function getKeys()
		{
			return array_keys($this->data);
		}

		public function itemAt($key)
		{
			if(isset($this->data[$key]))
				return $this->data[$key];
			else
				return null;
		}
		public function copyData($data)
		{
			if(is_array($data))
			{
				foreach($data as $key=>$value)
				{
					$this->add($key,$value);
				}
			}
		}
		public static function dataMerge($dataOne,$dataTwo)
		{
			foreach($dataTwo as $key=>$value)
			{
				if(is_integer($key))
					$dataOne[] = $value;
				elseif(isset($dataOne[$key]) && is_array($dataOne[$key]) && is_array($value))
					$dataOne[$key] = self::dataMerge($dataOne[$key],$value);
				else
					$dataOne[$key] = $value;
			}
		}
		public function getCount()
		{
			return count($this->data);
		}
		public function toArray()
		{
			return $this->data;
		}
		/*实现spl接口*/

		public function getIterator()
		{
			return new MapobIterator($this->data); 
		}

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

		public function offsetExists($offset)
		{
			return $this->data[$offset]!==null;
		}

		public function offsetGet($offset)
		{
			return $this->itemAt($offset);
		}

		public function offsetSet($offset,$item)
		{
			$this->add($offset,$item);
		}

		public function offsetUnset($offset)
		{
			$this->remove($offset);
		}
	}

	class MapobIterator implements Iterator
	{
		private $data = array();
		private $keys = array();
		public function __construct(&$data)
		{
			$this->data = &$data;
			$this->keys = array_keys($data);
		}

		public function rewind()
		{
			$this->key = reset($this->keys);
		}

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

		public function current()
		{
			return $this->data[$this->key];
		}

		public function next()
		{
			$this->key = next($this->keys);
		}

		public function valid()
		{
			return $this->key!==false;
		}
	}

	$a = new Mapob();
	$a->add('a','b');
	$a->add('b','c');
	$a->add('c','d');
	$a->add('d','e');
	foreach($a as $key=>$value)
	{
		echo $key;
		echo $value;
		echo "<br>";
	}