<?php 

$pids = []; //存储子进程pid
$MAX_PROCESS = 3;//最大进程数

$pid = pcntl_fork();
if($pid <0){
    exit("fork fail\n");
}elseif($pid > 0){
    exit;//父进程退出
}else{
    // 从当前终端分离
    if (posix_setsid() == -1) {
        die("could not detach from terminal");
    }

    $id = getmypid();   
    echo time()." Master process, pid {$id}\n"; 

    for($i=0; $i<$MAX_PROCESS;$i++){
        start_worker_process();
    }

    //Master进程等待子进程退出，必须是死循环
    while(1){
        foreach($pids as $pid){
            if($pid){
                $res = pcntl_waitpid($pid, $status, WNOHANG);
                if ( $res == -1 || $res > 0 ){
                    echo time()." Worker process $pid exit, will start new... \n";
                    start_worker_process();
                    unset($pids[$pid]);
                }
            }
        }
    }
}

/**
 * 创建worker进程
 */
function start_worker_process(){
    global $pids;
    $pid = pcntl_fork();
    if($pid <0){
        exit("fork fail\n");
    }elseif($pid > 0){
        $pids[$pid] = $pid;
        // exit; //此处不可退出，否则Master进程就退出了
    }else{
        //实际代码
        $id = getmypid();   
        $rand = rand(1,3);
        echo time()." Worker process, pid {$id}. run $rand s\n"; 
        while(1){
            sleep($rand);
        }
    }
}

<?php 

class TcpServer{
    const MAX_PROCESS = 3;//最大进程数
    private $pids = []; //存储子进程pid
    private $socket;

    public function __construct(){
        $pid = pcntl_fork();
        if($pid <0){
            exit("fork fail\n");
        }elseif($pid > 0){
            exit;//父进程退出
        } else{
            // 从当前终端分离
            if (posix_setsid() == -1) {
                die("could not detach from terminal");
            }

            umask(0);

            $id = getmypid();   
            echo time()." Master process, pid {$id}\n"; 

            //创建tcp server
            $this->socket = stream_socket_server("tcp://0.0.0.0:9201", $errno, $errstr);
            if(!$this->socket) exit("start server err: $errstr --- $errno");
        }
    }

    public function run(){
        for($i=0; $i<self::MAX_PROCESS;$i++){
            $this->start_worker_process();
        }

        echo "waiting client...\n";

        //Master进程等待子进程退出，必须是死循环
        while(1){
            foreach($this->pids as $k=>$pid){
                if($pid){
                    $res = pcntl_waitpid($pid, $status, WNOHANG);
                    if ( $res == -1 || $res > 0 ){
                        echo time()." Worker process $pid exit, will start new... \n";
                        $this->start_worker_process();
                        unset($this->pids[$k]);
                    }
                }
            }
            sleep(1);//让出1s时间给CPU
        }
    }

    /**
     * 创建worker进程，接受客户端连接
     */
    private function start_worker_process(){
        $pid = pcntl_fork();
        if($pid <0){
            exit("fork fail\n");
        }elseif($pid > 0){
            $this->pids[] = $pid;
            // exit; //此处不可退出，否则Master进程就退出了
        }else{
            $this->acceptClient();
        }
    }

    private function acceptClient()
    {
        //子进程一直等待客户端连接，不能退出
        while(1){
            $conn = stream_socket_accept($this->socket, -1);
            if($this->onConnect) call_user_func($this->onConnect, $conn); //回调连接事件

            //开始循环读取消息
            $recv = ''; //实际收到消息
            $buffer = ''; //缓冲消息
            while(1){
                $buffer = fread($conn, 20);

                //没有收到正常消息
                if($buffer === false || $buffer === ''){
                    if($this->onClose) call_user_func($this->onClose, $conn); //回调断开连接事件
                    break;//结束读取消息，等待下一个客户端连接
                }

                $pos = strpos($buffer, "\n"); //消息结束符
                if($pos === false){
                    $recv .= $buffer;                            
                }else{
                    $recv .= trim(substr($buffer, 0, $pos+1));

                    if($this->onMessage) call_user_func($this->onMessage, $conn, $recv); //回调收到消息事件

                    //客户端强制关闭连接
                    if($recv == "quit"){
                        echo "client close conn\n";
                        fclose($conn);
                        break;
                    }

                    $recv = ''; //清空消息，准备下一次接收
                }
            }
        }
    }

    function __destruct() {
        @fclose($this->socket);
    }
}

$server =  new TcpServer();

$server->onConnect = function($conn){
    echo "onConnect -- accepted " . stream_socket_get_name($conn,true) . "\n";
    fwrite($conn,"conn success\n");
};

$server->onMessage = function($conn,$msg){
    echo "onMessage --" . $msg . "\n";
    fwrite($conn,"received ".$msg."\n");
};

$server->onClose = function($conn){
    echo "onClose --" . stream_socket_get_name($conn,true) . "\n";
    fwrite($conn,"onClose "."\n");
};

$server->run();

$ ps -ef | grep php
yjc       9110     1  0 00:33 ?        00:00:00 php process_multi.server.php
yjc       9111  9110  0 00:33 ?        00:00:00 php process_multi.server.php
yjc       9112  9110  0 00:33 ?        00:00:00 php process_multi.server.php
yjc       9113  9110  0 00:33 ?        00:00:00 php process_multi.server.php
yjc       9134  8589  0 00:35 pts/1    00:00:00 grep php