mount = $mount;
		}
		public function getAmount(){
			return $this -> mount;
		}
		public function add($numbers = 200){
			return new self($this-> mount+$numbers);
		}
		public function debit($numbers = 200){
			if($this-> mount > $numbers){
				return new self($this-> mount - $numbers);
			}
			return false;
		}
	}
	/**
	 *	道具抽象类，规定了一些基本的道具所具有的共有的性质，例如拥有者、价格、
	 *  名称、游戏名称、可以出售、出租和购买，这些属性和方法都是属于道具共有
	 */
	abstract class Property{
		protected $name;
		protected $game;
		protected $price;
		protected $owner;
		function __construct($owner,$game,$name,$price){
			if(empty($owner)){echo '请输入道具的拥有者姓名
';return ;}
			echo '创建道具:所属游戏:'.$game.',名称：'.$name.',价格：'.$price.'
';
			$this->owner= $owner;
			$this->game = $game;
			$this->name = $name;
			$this->price =new Dollar($price);
		}
		/*道具的出租收取的租金，由具体的道具自己定义
			租金公式：$rent_num=$tax_rate * $price;
		*/
		abstract protected function calcRent();
		public function purcharse($player){
			global $owners;
			if($this-> owner ==$player-> name){
				echo '你已经购买了该道具
';
			}elseif($player -> salary->getAmount() < $this-> price-> getAmount() ){
				echo '金币不够
';
			}else{
				$flag=$player->debit($this->price->getAmount());
				if($flag){
					$price=$this->price->getAmount();
					$owners[$this->owner]->earnRent($price);
					unset($owners[$this->owner]);
					$this ->owner = $player->name;
					$owners[$this->owner]=$player;
					echo $player -> name.'购买道具:'.$this->game.$this->name.'成功
';
				}else{
					echo $player -> name.'购买道具:'.$this->game.$this->name.'失败
';
				}
			} 
		}
		public function __get($prop){
			if(isset($this->$prop)){
				return $this->$prop;
			}
		}
		public function setRent($player){
			global $owners;
			if($player->name==$this->owner){echo '不能租用自己的道具
';return ;}
			$price = $this-> calcRent();
			$player->debit($price);
			$owners[$this->owner]->earnRent($price);
			echo $player->name.'租用道具成功';
			return $price;
		}
		public function sell($player){
			global $owners;
			$price=$this->price->getAmount();
			if($player -> salary-> getAmount() > $price){
				echo '道具：'.$this-> game.$this->name.'-出售成功
';
				
				//这里实际上对应着数据库的更新操作
				$player->debit($price);
				$owners[$this->owner]->earnRent($price);
				unset($owners[$this->owner]);
				$this->owner = $player->name;
				$owners[$this->owner]=$player;
				return $price;
			}else{
				echo '道具出售失败
';
			}
		}
		public function __toString(){
			return $this->game.$this->owner.$this->name;
		}
	}
	//一个模拟的游戏玩家类
	class Player {
		public $salary;
		public $name;
		public function __construct($name){
			$this->salary = new Dollar(9000);
			$this->name = $name;
		}
		//支出
		public function debit($nums){
			$price= $this->salary ->getAmount();
			if($price < $nums){
				echo '钱包的钱不够了';
				return false;
			}
			$flag=$this->salary-> debit($nums);
			if($flag){
				$this->salary = $flag;
				return true;
			}else{
				return false;
			}
		}
		//收入
		public function earnRent($nums){
			$this->salary-> add($nums);
		}
	}
	//具体的道具类
	class Street extends Property{
		private $tax_rate=1;
		public function __construct($owner,$game,$name,$price,$tax_rate){
			parent::__construct($owner,$game,$name,$price);
			$this-> tax_rate = $tax_rate;	
		}
		//返回一个Dollar对象
		publ