状态模式

/**
* state模式
*
* 允许一个对象在其内部状态改变时改变它的行为,对象看起来似乎修改了它
所属的类
*
*/

    interface State
    {
        public function handle($state);
        public function display();
    }

    class Context
    {
        private $_state = null;
        
        public function __construct($state)
        {
            $this->setState($state);
        }
        
        public function setState($state)
        {
            $this->_state =$state;
        }
        
        public function request()
        {
            $this->_state->display();
            $this->_state->handle($this);
        }
    }

    class StateA implements State
    {
        public function handle($context)
        {
            $context->setState(new StateB());
        }
        
        public function display()
        {
            echo "state A<br/>";
        }
    }

    class StateB implements State
    {
        public function handle($context)
        {
            $context->setState(new StateC());
        }
        
        public function display()
        {
            echo"state B<br/>";
        }
    }

    class StateC implements State
    {
        public function handle($context)
        {
            $context->setState(new StateA());
        }
        
        public function display()
        {
            echo "state C<br/>";
        }
    }
    
// 实例化一下
$objContext = new Context(new StateB());
$objContext->request();//B
$objContext->request();//C
$objContext->request();//A
$objContext->request();//B
$objContext->request();//C

参考文章 https://wenku.baidu.com/view/b4c78b4702768e9951e738fb.html