谢邀.

如果你们有RabbitMQ的构架和经验, 实现这个很方便
rabbitmq 消息的消费端 channel 可以设置 prefetch=5, 即最多同时处理5条消息
rabbitmq 还有完善的ack机制, 即消息回执(该消息已正确处理完毕, 给我下条消息吧)
而且, 不会堵塞你当前PHP的进程, 后台(消费worker)会以5个并发的情形, 慢慢处理完这些任务

简单的可从Redis的List入手, 堵塞时判断队列的长度, 小于5时才开始popen并追加到队列

test.php

$redis = new \Redis();
$redis->connect("127.0.0.1", 6379);

$queue_name = "myqueue";
$queue_prefetch = 5;
$redis->delete($queue_name); // delete fro reseting.
for($i=0; $i<17; $i++){
    while(1){
        $count = count($redis->lRange($queue_name, 0, -1));
        if($count <= $queue_prefetch) break;
        usleep(20); // 堵塞20ms, 视情况而定, 太低redis I/O 会比较频繁
    }
    $redis->rPush($queue_name, $i);
    $pid = pcntl_fork(); // 开启子进程, 需要pcntl模块
    if($pid){
        pclose(popen("/usr/bin/php /diandao/script.php $i $pid $queue_name", "w"));
        pcntl_wait($status);
    }
}

/diandao/script.php

<?php
sleep(1); // 模拟处理超过1秒

$index = $argv[1];
$pid = $argv[2];
$queue = $argv[3];
$redis = new Redis;
$redis->connect("127.0.0.1", 6379);

$f = fopen("/diandao/script.log", "a+");
$date = date("Y-m-d H:i:s");
fwrite($f, "[$date] ".json_encode($argv).PHP_EOL );
fclose($f);
$redis->lRem($queue, $index);

/diandao/script.log 结果

数量判断那多写了个=号, 所以并发变成了6个

看到个帖子说到有个扩展可以实现子进程:Thread

大概描述了一下我的思路，这部分接触的不多，请多指教。

<?php
class Threads {
  protected $threads;
  protected $jobs;
  /**
   * Init Threads.
   *
   */
  public function __constructor($threadnum,$jobs)
  {
    $this->jobs = $jobs;
    for($i = 0;$i < $threadnum;$i++){
      $this->threads[$i] = new childThread();
    }
    $this->doJob();
  }
  /**
   * scan the thread.
   *
   * @return bool|@thread
   */
  public function scan()
  {
    if(count($this->jobs) <=0)
      return 'no jobs!';
    foreach($this->threads as $key => $obj)
    {
      if($obj->busy === false)
      {
        $idleThreads[] = $obj;
      }
    }
    if(count($idleThreads)>0)
    {
      $this->doJob($idleThreads);
      return false;
    }
    else
    { 
      return false;
    }
  }
  protected function doJob($idleThreads){
    foreach($idleThreads as $id => $thread){
      $thread->job = $this->getJob();
      $thread->start();
    }
  }
  protected function getJob(){
    $r = $this->jobs[0];
    unset($this->jobs[0]);
    return $r;
  }
  
}
class childThread extends Thread{
  public $job;
  public $busy=false;
  public function run(){
    //set busy=true
    $this->busy = true;
    //do job!

    //set busy=false
    $this->busy = false;
  }
}
//script:

$pool = new Threads(5,array(1,2,3...17));
while(1){
  if($pool->scan() == 'no jobs!'){
    exit();
  }else{
    sleep(1000);
  }
}

谢邀，这个感觉是进程池的概念吧。

谢邀。

popen是异步的，不会出现阻塞啊。理论上不会等一个线程结束才开始另一个线程的。