如何使用cURL与PHP同时打开多个URL？

Question

这里是我当前的代码：

$SQL = mysql_query("SELECT url FROM urls") or die(mysql_error()); //Query the urls table 
while($resultSet = mysql_fetch_array($SQL)){ //Put all the urls into one variable 

       // Now for some cURL to run it. 
      $ch = curl_init($resultSet['url']); //load the urls 
      curl_setopt($ch, CURLOPT_TIMEOUT, 2); //No need to wait for it to load. Execute it and go. 
      curl_exec($ch); //Execute 
      curl_close($ch); //Close it off 
     } //While loop 

我是比较新的卷曲。相对较新，我的意思是这是我第一次使用cURL。目前它加载一个两秒，然后加载下一个2秒，然后下一个。不过，我想让它在同一时间加载它们。我相信它是可能的，我只是不确定如何。如果有人能指引我正确的方向，我会很感激。

Answer 1

您以相同的方式设置每个cURL句柄，然后将它们添加到curl_multi_句柄。要查看的功能是curl_multi_*函数documented here。不过，根据我的经验，尝试一次加载过多网址时存在问题（尽管目前我无法在其上找到我的笔记），所以上次我使用curl_mutli_时，我将其设置为分批每次5个网址。

编辑：这是我一直在使用curl_multi_代码的简化版本：

编辑：略改写和大量的补充意见，希望这将有助于。

// -- create all the individual cURL handles and set their options 
$curl_handles = array(); 
foreach ($urls as $url) { 
    $curl_handles[$url] = curl_init(); 
    curl_setopt($curl_handles[$url], CURLOPT_URL, $url); 
    // set other curl options here 
} 

// -- start going through the cURL handles and running them 
$curl_multi_handle = curl_multi_init(); 

$i = 0; // count where we are in the list so we can break up the runs into smaller blocks 
$block = array(); // to accumulate the curl_handles for each group we'll run simultaneously 

foreach ($curl_handles as $a_curl_handle) { 
    $i++; // increment the position-counter 

    // add the handle to the curl_multi_handle and to our tracking "block" 
    curl_multi_add_handle($curl_multi_handle, $a_curl_handle); 
    $block[] = $a_curl_handle; 

    // -- check to see if we've got a "full block" to run or if we're at the end of out list of handles 
    if (($i % BLOCK_SIZE == 0) or ($i == count($curl_handles))) { 
     // -- run the block 

     $running = NULL; 
     do { 
      // track the previous loop's number of handles still running so we can tell if it changes 
      $running_before = $running; 

      // run the block or check on the running block and get the number of sites still running in $running 
      curl_multi_exec($curl_multi_handle, $running); 

      // if the number of sites still running changed, print out a message with the number of sites that are still running. 
      if ($running != $running_before) { 
       echo("Waiting for $running sites to finish...\n"); 
      } 
     } while ($running > 0); 

     // -- once the number still running is 0, curl_multi_ is done, so check the results 
     foreach ($block as $handle) { 
      // HTTP response code 
      $code = curl_getinfo($handle, CURLINFO_HTTP_CODE); 

      // cURL error number 
      $curl_errno = curl_errno($handle); 

      // cURL error message 
      $curl_error = curl_error($handle); 

      // output if there was an error 
      if ($curl_error) { 
       echo(" *** cURL error: ($curl_errno) $curl_error\n"); 
      } 

      // remove the (used) handle from the curl_multi_handle 
      curl_multi_remove_handle($curl_multi_handle, $handle); 
     } 

     // reset the block to empty, since we've run its curl_handles 
     $block = array(); 
    } 
} 

// close the curl_multi_handle once we're done 
curl_multi_close($curl_multi_handle); 

既然你什么都不需要从后面的网址，你也许并不需要很多东西的存在，但我这是怎么分块请求进入BLOCK_SIZE块，等待每块在继续之前运行，并从cURL中捕获错误。