<?php

// 处理者接口
interface Handler {
    public function handleRequest($request);
}

// 具体处理者1
class ConcreteHandler1 implements Handler {
    private $successor;

    public function setSuccessor(Handler $successor) {
        $this->successor = $successor;
    }

    public function handleRequest($request) {
        if ($request == "Type1") {
            echo "ConcreteHandler1 handles the request.\n";
        } elseif ($this->successor !== null) {
            // 转发请求给下一个处理者
            $this->successor->handleRequest($request);
        } else {
            echo "ConcreteHandler1 cannot handle the request.\n";
        }
    }
}

// 具体处理者2
class ConcreteHandler2 implements Handler {
    private $successor;

    public function setSuccessor(Handler $successor) {
        $this->successor = $successor;
    }

    public function handleRequest($request) {
        if ($request == "Type2") {
            echo "ConcreteHandler2 handles the request.\n";
        } elseif ($this->successor !== null) {
            // 转发请求给下一个处理者
            $this->successor->handleRequest($request);
        } else {
            echo "ConcreteHandler2 cannot handle the request.\n";
        }
    }
}

// 客户端代码
$handler1 = new ConcreteHandler1();
$handler2 = new ConcreteHandler2();

$handler1->setSuccessor($handler2);

// 向第一个处理者发送请求
$handler1->handleRequest("Type1");
$handler1->handleRequest("Type2");
$handler1->handleRequest("Type3");