server:

class Server
{
    private $_serv = null;

    private $_workers = [];

    private $_worker_num = 2;

    public function __construct()
    {
        $this->_serv = new swoole_server('127.0.0.1', 9501);

        $this->_serv->on('start', array($this, 'onStart'));
        $this->_serv->on('workerstart', array($this, 'onWorkerStart'));
        $this->_serv->on('connect', array($this, 'onConnect'));
        $this->_serv->on('receive', array($this, 'onReceive'));
        $this->_serv->on('close', array($this, 'onClose'));

        $this->_serv->start();
    }

    public function onStart($serv)
    {
        echo "start \n";
    }

    public function onWorkerStart($serv, $worker_id)
    {
        echo "worker start\n";
    }
    
    public function onConnect($serv, $fd, $from_id )
    {
        echo "connect..\n";
    }

    public function onReceive(swoole_server $serv, $fd, $from_id, $data)
    {

        for ($i = 0; $i < $this->_worker_num ;$i++) {
            $process = new swoole_process(array($this, 'onProcess'), false, false);
            $process->useQueue();
            $pid = $process->start();
            echo $pid;
            $this->_workers[$pid] = $process;
        }

        foreach ($this->_workers as $pid => $worker) {
            echo $process->push("hello worker[{$pid}]\n");
            sleep(2);//停2秒，不然主进程pop时 获取消息太快，而阻塞状态了，push完给子进程消息，子进程逻辑还没处理完
            //(1)不加这停两秒时，可能主进程马上pop时，队列是空的，主进程阻塞状态了，下面子进程只能pop和push一次，再pop时也阻塞状态了
            //客户端再发send消息时,服务器不响应，除非新client进来，发send，主进程阻塞取消了，第一个客户端又可以发send消息了，第二个客户端
            //发send消息时，服务端不响应，这种情况发生了
            
$result = $process->pop();//默认模式下，如果队列中没有数据，pop方法会阻塞等待
            echo "From worker: $result\n";//这里主进程，接受到的子进程的数据
        }

        for($i = 0; $i < $this->_worker_num; $i++)
        {
            $ret = swoole_process::wait();
            $pid = $ret['pid'];
            unset($this->_workers[$pid]);
            echo "Worker Exit, PID=".$pid.PHP_EOL;
        }

    }

    public function onProcess($worker)
    {
        $msg_status = $worker->statQueue();
        if($msg_status['queue_num'] > 0)
        {
            $recv = $worker->pop();

            echo "FROM master {$recv}\n";
            $worker->push("heheh parent");//子进程处理完逻辑，不是马上push数据给主进程  sleep(2)
        }
        $worker->exit(0);

    }

    public function onClose($serv, $fd, $from_id)
    {
        echo "close.\n";
    }
}

new Server();

client:

$cli = new Swoole_client(SWOOLE_SOCK_TCP);

$cli->connect('127.0.0.1', 9501, 1);

fwrite(STDOUT, '输入消息：');
$msg = trim(fgets(STDIN));

echo $cli->send($msg);

echo $cli->recv()."\n";