责任链模式

<?php  
	class Admin{
		public $top="";
		public $level=0;
		public function __construct(){ }

		public function ToDo(){}

		public function deal($level){
			if($level <= $this->level){
				//如果当前类能够解决问题，则直接让当前类解决，不用传递给上级
				$this->ToDo();
			} else {
				//如果当前类的等级不够（不能解决问题），则将问题传递给上一级
				//即生成一个上级类，然后调用上级类的方法来解决问题，层层深入，直到解决问题
				//top属性初始为上级类名
				//将新生成的上级类的实例化对象赋给top属性
				$this->top= new $this->top;
				$this->top->deal($level);
			}
		}
	}

	class PersonOne extends Admin{
		public $level=1;
		public $top="PersonTwo";
		public function ToDo(){
			echo "the problem has been solved by PersonOne\n";
		}
	}

	class PersonTwo extends Admin{
		public $level=2;
		public $top="PersonThree";
		public function ToDo(){
			echo "the problem has been solved by PersonTwo\n";
		}
	}

	class PersonThree extends Admin{
		public $level=3;
		public $top=__CLASS__;
		public function ToDo(){
			echo "the problem has been solved by PersonThree\n";
		}

	}

	$level=1;
	$d=new PersonOne();
	$d->deal($level);

	$level=2;
	$d=new PersonOne();
	$d->deal($level);

	$level=3;
	$d=new PersonOne();
	$d->deal($level);
?>