swoole到底可以多线程么

<?php
/**
 * 创建多进程
 */
$worker_num = 6; // 默认进程数
$workers = []; // 进程保存
$redirect_stdout = false; // 重定向输出 ; 这个参数用途等会我们看效果
for($i = 0; $i < $worker_num; $i++){
 $process = new swoole_process('callback_function', $redirect_stdout);
 
 // 启用消息队列 int $msgkey = 0, int $mode = 2
 $process->useQueue(0, 2);
 $pid = $process->start();
 
 // 管道写入内容
 $process->write('index:'.$i);
 
 $process->push('进程的消息队列内容');
 // 将每一个进程的句柄存起来
 $workers[$pid] = $process;
}
 
 
/**
 * 子进程回调
 * @param swoole_process $worker [description]
 * @return [type] [description]
 */
function callback_function(swoole_process $worker)
{
 $recv = $worker->pop();
 echo "子输出主内容: {$recv}".PHP_EOL;
 //get guandao content
 $recv = $worker->read();
 $result = doTask();
 
 echo PHP_EOL.$result.'==='.$worker->pid.'==='.$recv;
 
 $worker->exit(0);
}
 
 
/**
 * 监控/回收子进程
 */
while(1){
 $ret = swoole_process::wait();
 if ($ret){// $ret 是个数组 code是进程退出状态码，
 $pid = $ret['pid'];
 echo PHP_EOL."Worker Exit, PID=" . $pid . PHP_EOL;
 }else{
 break;
 }
}
 
 
/**
 * doTask
 * @return [type] [description]
 */
function doTask()
{
 sleep(2);
 return true;
}