Example of how PHP uses curl_multi to implement concurrent requests

class CurlMultiUtil {
  /**
  * 根据url,postData获取curl请求对象,这个比较简单,可以看官方文档
  */
  private static function getCurlObject($url,$postData=array(),$header=array()){
    $options = array();
    $url = trim($url);
    $options[CURLOPT_URL] = $url;
    $options[CURLOPT_TIMEOUT] = 3;
    $options[CURLOPT_RETURNTRANSFER] = true;
    foreach($header as $key=>$value){
      $options[$key] =$value;
    }
    if(!empty($postData) && is_array($postData)){
      $options[CURLOPT_POST] = true;
      $options[CURLOPT_POSTFIELDS] = http_build_query($postData);
    }
    if(stripos($url,'https') === 0){
      $options[CURLOPT_SSL_VERIFYPEER] = false;
    }
    $ch = curl_init();
    curl_setopt_array($ch,$options);
    return $ch;
  }
  /**
   * [request description]
   * @param [type] $chList
   * @return [type]
   */
  private static function request($chList){
    $downloader = curl_multi_init();
    // 将三个待请求对象放入下载器中
    foreach ($chList as $ch){
      curl_multi_add_handle($downloader,$ch);
    }
    $res = array();
    // 轮询
    do {
      while (($execrun = curl_multi_exec($downloader, $running)) == CURLM_CALL_MULTI_PERFORM);
      if ($execrun != CURLM_OK) {
        break;
      }
      // 一旦有一个请求完成，找出来，处理,因为curl底层是select，所以最大受限于1024
      while ($done = curl_multi_info_read($downloader)){
        // 从请求中获取信息、内容、错误
        // $info = curl_getinfo($done['handle']);
        $output = curl_multi_getcontent($done['handle']);
        // $error = curl_error($done['handle']);
        $res[] = $output;
        // 把请求已经完成了得 curl handle 删除
        curl_multi_remove_handle($downloader, $done['handle']);
      }
      // 当没有数据的时候进行堵塞，把 CPU 使用权交出来，避免上面 do 死循环空跑数据导致 CPU 100%
      if ($running) {
        $rel = curl_multi_select($downloader, 1);
        if($rel == -1){
          usleep(1000);
        }
      }
      if($running == false){
        break;
      }
    }while(true);
    curl_multi_close($downloader);
    return $res;
  }
  /**
   * [get description]
   * @param [type] $urlArr
   * @return [type]
   */
  public static function get($urlArr){
    $data = array();
    if (!empty($urlArr)) {
      $chList = array();
      foreach ($urlArr as $key => $url) {
        $chList[] = self::getCurlObject($url);
      }
      $data = self::request($chList);
    }
    return $data;
  }
}