使用PHP并行下载页面

当我听到有人使用curl_multi_exec时,通常会发现他们只是用100个网址加载它,然后在完成后等待,然后全部处理它们,然后用接下来的100个网址重新开始…怪我,我是这样做,但后来我发现有可能在某些事情仍在进行时删除/添加curl_multi的句柄,并且它确实节省了大量时间,特别是如果你重用已经打开的连接.我写了一个小型库来处理带回调的请求队列;我当然不是在这里发布完整版本(“小”仍然是相当多的代码),但这里有一个简化版本,主要给你一般的想法：

public function launch() {
    $channels = $freeChannels = array_fill(0,$this->maxConnections,NULL);
    $activeJobs = array();
    $running = 0;
    do {
        // pick jobs for free channels:
        while ( !(empty($freeChannels) || empty($this->jobQueue)) ) {
            // take free channel,(re)init curl handle and let
            // queued object set options
            $chId = key($freeChannels);
            if (empty($channels[$chId])) {
                $channels[$chId] = curl_init();
            }
            $job = array_pop($this->jobQueue);
            $job->init($channels[$chId]);
            curl_multi_add_handle($this->master,$channels[$chId]);
            $activeJobs[$chId] = $job;
            unset($freeChannels[$chId]);
        }
        $pending = count($activeJobs);

        // launch them:
        if ($pending > 0) {
            while(($mrc = curl_multi_exec($this->master,$running)) == CURLM_CALL_MULTI_PERFORM);
                // poke it while it wants
            curl_multi_select($this->master);
                // wait for some activity,don't eat cpu
            while ($running < $pending && ($info = curl_multi_info_read($this->master))) {
                // some connection(s) finished,locate that job and run response handler:
                $pending--;
                $chId = array_search($info['handle'],$channels);
                $content = curl_multi_getcontent($channels[$chId]);
                curl_multi_remove_handle($this->master,$channels[$chId]);
                $freeChannels[$chId] = NULL;
                    // free up this channel
                if ( !array_key_exists($chId,$activeJobs) ) {
                    // impossible,but...
                    continue;
                }
                $activeJobs[$chId]->onComplete($content);
                unset($activeJobs[$chId]);
            }
        }
    } while ( ($running > 0 && $mrc == CURLM_OK) || !empty($this->jobQueue) );
}

在我的版本中,$jobs实际上是单独的类,而不是控制器或模型的实例.他们只处理设置cURL选项,解析响应并调用给定的回调onComplete.
使用此结构,只要池中的某些内容完成,新请求就会立即启动.

当然,如果不只是检索需要时间而且处理也不会真正拯救你……而且它并不是真正的并行处理.但我仍然希望它有所帮助.