设计模式(20)state模式

class Context {
  protected $state;
  public function setState($s){
    $this->state = $s;
  }
  public function request(){
    $this->state->handle();
  }
}
abstract class State{
  abstract function handle();
}
class ConcreteStateA extends State{
  protected $context;
  function __construct($context){
    $this->context = $context;
  }
  function handle(){
    echo "this is stateA";
    $this->context->setState(new ConcreteStateB($this->context));
  }

}
class ConcreteStateB extends State{
  protected $context;
  function __construct($context){
    $this->context = $context;
  }
  function handle(){
    echo "this is stateB";
  }
}
//测试代码
$context = new Context();
$context->setState(new ConcreteStateA($context));
$context->request();
$context->request();