大话设计模式第十六章--状态模式

<?php
abstract class State {
    abstract public function handle(Context $context);
}

class Concrete_state_A extends State {
    public function handle(Context $context) {
        echo "NOW IS IN STATE_A <br/>";
        $context->state = new Concrete_state_B();
    }
}

class Concrete_state_B extends State {
    public function handle(Context $context) {
        echo "NOW IS IN STATE_B <br/>";
        $context->state = new Concrete_state_A();
    }
}

class Context {
    private $state;
    public function __construct(State $state) {
        $this->state = $state;
    }
    public function __get($param) {
        if ($param == ‘state‘) {
            return $this->state;
        }
    }
    public function __set($param, $state) {
        if ($param == ‘state‘) {
            $this->state = $state;
        }
    }

    public function request() {
        $this->state->handle($this);
    }
}

//CLIENT CODE
$c = new Context(new Concrete_state_A());
$c->request();
$c->request();
$c->request();
$c->request();