php实现发布订阅

发布订阅模式简介

发布订阅模式是一种消息通信模式，发布者将消息发送到特定频道，订阅者接收感兴趣频道的消息，双方无需直接交互。PHP可通过多种方式实现该模式。

使用Redis实现

Redis内置发布订阅功能，PHP可通过predis或phpredis扩展操作：

安装predis库：

composer require predis/predis

发布消息示例代码：

<?php
require 'vendor/autoload.php';
$client = new Predis\Client();
$client->publish('channel_name', 'message_content');

订阅消息示例代码：

<?php
require 'vendor/autoload.php';
$client = new Predis\Client();
$pubsub = $client->pubSubLoop();
$pubsub->subscribe('channel_name');

foreach ($pubsub as $message) {
    if ($message->kind === 'message') {
        echo "Received: {$message->payload}\n";
    }
}

使用RabbitMQ实现

RabbitMQ是专业消息队列系统，支持更复杂的发布订阅场景：

安装PHP-AMQP扩展：

pecl install amqp

发布者代码示例：

<?php
$connection = new AMQPConnection(['host' => 'localhost']);
$connection->connect();
$channel = new AMQPChannel($connection);
$exchange = new AMQPExchange($channel);
$exchange->setName('logs');
$exchange->setType(AMQP_EX_TYPE_FANOUT);
$exchange->publish('message content');

订阅者代码示例：

<?php
$connection = new AMQPConnection(['host' => 'localhost']);
$connection->connect();
$channel = new AMQPChannel($connection);
$exchange = new AMQPExchange($channel);
$exchange->setName('logs');
$exchange->setType(AMQP_EX_TYPE_FANOUT);
$queue = new AMQPQueue($channel);
$queue->setFlags(AMQP_EXCLUSIVE);
$queue->declareQueue();
$queue->bind('logs');
while (true) {
    if ($message = $queue->get()) {
        echo $message->getBody();
        $queue->ack($message->getDeliveryTag());
    }
}

纯PHP实现简易版本

对于简单场景可基于SplSubject和SplObserver接口：

主题类实现：

class Topic implements SplSubject {
    private $observers = [];
    private $message;

    public function attach(SplObserver $observer) {
        $this->observers[] = $observer;
    }

    public function notify() {
        foreach ($this->observers as $observer) {
            $observer->update($this);
        }
    }

    public function publish($message) {
        $this->message = $message;
        $this->notify();
    }
}

观察者实现：

class Subscriber implements SplObserver {
    public function update(SplSubject $subject) {
        echo "Received: " . $subject->message . "\n";
    }
}

使用示例：

$topic = new Topic();
$topic->attach(new Subscriber());
$topic->publish("test message");

性能与选择建议

Redis适合轻量级、高频场景，RabbitMQ适合需要持久化、复杂路由的场景，纯PHP实现适合进程内通信。生产环境建议使用专业消息中间件，注意消息确认机制和异常处理。