curl_multi_exec()

(PHP 5, PHP 7)

运行当前 cURL 句柄的子连接

说明

curl_multi_exec(resource $mh,int &$still_running): int

处理在栈中的每一个句柄。无论该句柄需要读取或写入数据都可调用此方法。

参数

$mh

由curl_multi_init()返回的 cURL 多个句柄。

$still_running

一个用来判断操作是否仍在执行的标识的引用。

返回值

一个定义于 cURL 预定义常量中的 cURL 代码。

Note:

该函数仅返回关于整个批处理栈相关的错误。即使返回CURLM_OK时单个传输仍可能有问题。

范例

curl_multi_exec() example

这个范例将会创建 2 个 cURL 句柄，把它们加到批处理句柄，然后并行地运行它们。

<?php
// 创建一对cURL资源
$ch1 = curl_init();
$ch2 = curl_init();
// 设置URL和相应的选项
curl_setopt($ch1, CURLOPT_URL, "http://lxr.php.net/");
curl_setopt($ch1, CURLOPT_HEADER, 0);
curl_setopt($ch2, CURLOPT_URL, "http://www.php.net/");
curl_setopt($ch2, CURLOPT_HEADER, 0);
// 创建批处理cURL句柄
$mh = curl_multi_init();
// 增加2个句柄
curl_multi_add_handle($mh,$ch1);
curl_multi_add_handle($mh,$ch2);
$active = null;
// 执行批处理句柄
do {
    $mrc = curl_multi_exec($mh, $active);
} while ($mrc == CURLM_CALL_MULTI_PERFORM);
while ($active && $mrc == CURLM_OK) {
    if (curl_multi_select($mh) != -1) {
        do {
            $mrc = curl_multi_exec($mh, $active);
        } while ($mrc == CURLM_CALL_MULTI_PERFORM);
    }
}
// 关闭全部句柄
curl_multi_remove_handle($mh, $ch1);
curl_multi_remove_handle($mh, $ch2);
curl_multi_close($mh);
?>

参见

• curl_multi_init()返回一个新cURL批处理句柄
• curl_multi_select()等待所有cURL批处理中的活动连接
• curl_exec()执行 cURL 会话

Solve CPU 100% usage, a more simple and right way:
<?php
do {
  curl_multi_exec($mh, $running);
  curl_multi_select($mh);
} while ($running > 0);
?>

Probably you also want to be able to download the HTML content into buffers/variables, for parsing the HTML or for other processing in your program.
The example code on this page only outputs everything on the screen, without giving you the possibility to save the downloaded pages in string variables. Because downloading multiple pages is what I wanted to do (not a big surprise, huh? that's the reason for using multi-page parallel Curl) I was initially baffled, because this page doesn't give pointers to a guide how to do that.
Fortunately, there's a way to download content with parallel Curl requests (just like you would do for a single download with the regular curl_exec). You need to use: http://php.net/manual/en/function.curl-multi-getcontent.php
The function curl_multi_getcontent should definitely be mentioned in the "See Also" section of curl_multi_exec. Probably most people who find their way to the docs page of curl_multi_exec, actually want to download the multiple HTML pages (or other content from the multiple parallel Curl connections) into buffers, one page per one buffer.

// Todas url gravadas em array
$url[] = 'http://www.link1.com.br';
$url[] = 'https://www.link2.com.br';
$url[] = 'https://www.link3.com.br';
// Setando opção padrão para todas url e adicionando a fila para processamento
$mh = curl_multi_init();
foreach($url as $key => $value){
 $ch[$key] = curl_init($value);
 curl_setopt($ch[$key], CURLOPT_NOBODY, true);
 curl_setopt($ch[$key], CURLOPT_HEADER, true);
 curl_setopt($ch[$key], CURLOPT_RETURNTRANSFER, true);
 curl_setopt($ch[$key], CURLOPT_SSL_VERIFYPEER, false);
 curl_setopt($ch[$key], CURLOPT_SSL_VERIFYHOST, false);
 
 curl_multi_add_handle($mh,$ch[$key]);
}
// Executando consulta
do {
 curl_multi_exec($mh, $running);
 curl_multi_select($mh);
} while ($running > 0);
// Obtendo dados de todas as consultas e retirando da fila
foreach(array_keys($ch) as $key){
 echo curl_getinfo($ch[$key], CURLINFO_HTTP_CODE);
 echo curl_getinfo($ch[$key], CURLINFO_EFFECTIVE_URL);
 echo "\n";
 
 curl_multi_remove_handle($mh, $ch[$key]);
}
// Finalizando
curl_multi_close($mh);

Just for people struggling to get this to work, here is my approach.
No infinite loops, no CPU 100%, speed can be tweaked.
<?php
function curl_multi_exec_full($mh, &$still_running) {
  do {
    $state = curl_multi_exec($mh, $still_running);
  } while ($still_running > 0 && $state === CURLM_CALL_MULTI_PERFORM && curl_multi_select($mh, 0.1));
  return $state;
}
function curl_multi_wait($mh, $minTime = 0.001, $maxTime = 1){
  $umin = $minTime*1000000;
  $start_time = microtime(true);
  $num_descriptors = curl_multi_select($mh, $maxTime);
  if($num_descriptors === -1){
    usleep($umin);
  }
  $timespan = (microtime(true) - $start_time);
  if($timespan < $umin){
    usleep($umin - $timespan);
  }
}
$handles = [
  [
    CURLOPT_URL=>"http://example.com/",
    CURLOPT_HEADER=>false,
    CURLOPT_RETURNTRANSFER=>true,
    CURLOPT_FOLLOWLOCATION=>false,
  ],
  [
    CURLOPT_URL=>"http://www.php.net",
    CURLOPT_HEADER=>false,
    CURLOPT_RETURNTRANSFER=>true,
    CURLOPT_FOLLOWLOCATION=>false,
    // https://stackoverflow.com/a/41135574
    CURLOPT_HEADERFUNCTION=>function($ch, $header)
    {
      print "header from http://www.php.net: ".$header;
      return strlen($header);
    }
  ]
];
$mh = curl_multi_init();
$chandles = [];
foreach($handles as $opts) {
  $ch = curl_init();
  curl_setopt_array($ch, $opts);
  curl_multi_add_handle($mh, $ch);
  $chandles[] = $ch;
}
$prevRunning = null;
do {
  $status = curl_multi_exec_full($mh, $running);
  if($running < $prevRunning){
    while ($read = curl_multi_info_read($mh, $msgs_in_queue)) {
      $info = curl_getinfo($read['handle']);
      if($read['result'] !== CURLE_OK){
        print "Error: ".$info['url'].PHP_EOL;
      }
      if($read['result'] === CURLE_OK){
        /*
        if(isset($info['redirect_url']) && trim($info['redirect_url'])!==''){
          print "running redirect: ".$info['redirect_url'].PHP_EOL;
          $ch3 = curl_init();
          curl_setopt($ch3, CURLOPT_URL, $info['redirect_url']);
          curl_setopt($ch3, CURLOPT_HEADER, 0);
          curl_setopt($ch3, CURLOPT_RETURNTRANSFER, 1);
          curl_setopt($ch3, CURLOPT_FOLLOWLOCATION, 0);
          curl_multi_add_handle($mh,$ch3);
        }
        */
        print_r($info);
        //echo curl_multi_getcontent($read['handle']));
      }
    }
  }
  if ($running > 0) {
    curl_multi_wait($mh);
  }
  $prevRunning = $running;
} while ($running > 0 && $status == CURLM_OK);
foreach($chandles as $ch){
  curl_multi_remove_handle($mh, $ch);
}
curl_multi_close($mh);
?>

http://curl.haxx.se/libcurl/c/libcurl-multi.html
"When you've added the handles you have for the moment (you can still add new ones at any time), you start the transfers by call curl_multi_perform(3).
curl_multi_perform(3) is asynchronous. It will only execute as little as possible and then return back control to your program. It is designed to never block. If it returns CURLM_CALL_MULTI_PERFORM you better call it again soon, as that is a signal that it still has local data to send or remote data to receive."
So it seems the loop in sample script should look this way:
<?php
$running=null;
//execute the handles
do {
  while (CURLM_CALL_MULTI_PERFORM === curl_multi_exec($mh, $running));
  if (!$running) break;
  while (($res = curl_multi_select($mh)) === 0) {};
  if ($res === false) {
    echo "<h1>select error</h1>";
    break;
  }
} while (true);
?>
This worked fine (PHP 5.2.5 @ FBSD 6.2) without running non-blocked loop and wasting CPU time.
However this seems to be the only use of curl_multi_select, coz there's no simple way to bind it with other PHP wrappers for select syscall.

I tried Daniel G Zylberberg's function and
it was not working the way it was posted.
I made some changes to get it work and here is what I use:
function multiCurl($res, $options=""){
    if(count($res)<=0) return False;
    $handles = array();
    if(!$options) // add default options
      $options = array(
        CURLOPT_HEADER=>0,
        CURLOPT_RETURNTRANSFER=>1,
      );
    // add curl options to each handle
    foreach($res as $k=>$row){
      $ch{$k} = curl_init();
      $options[CURLOPT_URL] = $row['url'];
      $opt = curl_setopt_array($ch{$k}, $options);
      var_dump($opt);
      $handles[$k] = $ch{$k};
    }
    $mh = curl_multi_init();
    // add handles
    foreach($handles as $k => $handle){
      $err = curl_multi_add_handle($mh, $handle);      
    }
    $running_handles = null;
    do {
     curl_multi_exec($mh, $running_handles);
     curl_multi_select($mh);
    } while ($running_handles > 0);
    
    foreach($res as $k=>$row){
      $res[$k]['error'] = curl_error($handles[$k]);
      if(!empty($res[$k]['error']))
        $res[$k]['data'] = '';
      else
        $res[$k]['data'] = curl_multi_getcontent( $handles[$k] ); // get results
      // close current handler
      curl_multi_remove_handle($mh, $handles[$k] );
    }
    curl_multi_close($mh);
    return $res; // return response
}

This example is not fully working on PHP5.6.
Using curl_multi, and CURLOPT_VERBOSE & CURLOPT_STDERR, If found that sending curl_multi request before any "classic" cURL request will result in timeout error against some hostname. The error message display
  > * Hostname was NOT found in DNS cache
It seems that that adding this line to the first loop solve this problem.
    do {
      $mrc = curl_multi_exec($mh, $active);
      // check errors
      if ($mrc > 0) {
        // display error
        error_log(curl_multi_strerror($mrc));
      }
    } while ($mrc === CURLM_CALL_MULTI_PERFORM || $active);
source : https://stackoverflow.com/questions/30935541/php-curl-error-hostname-was-not-found-in-dns-cache

当在OS X mavericks中运行curl_multi_exec()时，
可能会得不到想要的结果，
因为脚本会一直执行但是却没有返回值，
这是因为在OS X中当php在5.3.8以上版本时，
在调用curl_multi_exec()方法之前curl_multi_select()会一直返回-1，
所以这里改写一下脚本，
可以在OS X中成功执行：
<?php
$ch1 = curl_init();
$ch2 = curl_init();
// 设置URL和相应的选项
curl_setopt($ch1, CURLOPT_URL, "http://lxr.php.net");
curl_setopt($ch1, CURLOPT_HEADER, 0);
curl_setopt($ch2, CURLOPT_URL, "http://www.php.net");
curl_setopt($ch2, CURLOPT_HEADER, 0);
// 创建批处理cURL句柄
$mh = curl_multi_init();
// 增加2个句柄
curl_multi_add_handle($mh,$ch1);
curl_multi_add_handle($mh,$ch2);
$active = null;
do {
  $mrc = curl_multi_exec($mh, $active);
} while ($mrc == CURLM_CALL_MULTI_PERFORM);
while ($active && $mrc == CURLM_OK) 
{  
  // add this line
  while (curl_multi_exec($mh, $active) === CURLM_CALL_MULTI_PERFORM);
  if (curl_multi_select($mh) != -1) 
  {  
    do {
      $mrc = curl_multi_exec($mh, $active);
      if ($mrc == CURLM_OK)
      {  
        while($info = curl_multi_info_read($mh))
        {  
          var_dump($info);
        }    
      }  
    } while ($mrc == CURLM_CALL_MULTI_PERFORM);
  }  
}
 //close the handles
curl_multi_remove_handle($mh, $ch1);
curl_multi_remove_handle($mh, $ch2);
curl_multi_close($mh);
?>

/!\ ATTENTION
/!\ Several of the non-downvoted notes on this page are using outdated info.
The CURLM_CALL_MULTI_PERFORM return code has been defunct since circa 2012, at least seven years ago.
Quoting the author of curl, from https://curl.haxx.se/mail/lib-2012-08/0042.html:
> CURLM_CALL_MULTI_PERFORM is deprecated and will never be returned, as documented. 
> During the first decade or so of libcurl's multi interface, I never saw a single proper use of that feature. I did however see numerous mistakes and misunderstandings. That made me decide that the feature wasn't important or good enough, so since 7.20.0 CURLM_CALL_MULTI_PERFORM is no more. 
Discovered all of this thanks to https://stackoverflow.com/q/19490837/3229684, which suggested the following replacement while loop:
<?php
do {
  $mrc = curl_multi_exec($mc, $active);
} while ($active > 0);
?>
https://www.google.com/search?q=CURLM_CALL_MULTI_PERFORM <-- probably the most future-proof useful link I can put here

This example not working on window 7 with php version 5.3.27.

Here's something that had me pulling my hair out for quite a while. I was trying to download multiple files and save each one in a file. If you want to read the file again in the same script that has downloaded the url, always make sure to close the original filehandle that you opened for the connection BEFORE trying to read from the file again, even if you open a new filehandle to do so. If you don't do this, a file_get_contents() or fread() will cut your file and only return a limited size of it, 40960 characters in my case, without any other explanation or error. The file will exist (and be complete) on your disk, PHP just wont show it.
I (perhaps mistakenly) thought this was a bug so I created a bug report, see it for examples of the code I used to recreate this misterious behavior:
https://bugs.php.net/bug.php?id=62409

> replying to viczbk.ru
Just sharing my attempt at it.
> while (($res = curl_multi_select($mh)) === 0) {};
This worked on my windows computer (php 5.2.5) but when I ran the curl program in my new centOS server (php 5.1.6) the function never updates unless curl_multi_exec() is added to the loop, taking away the point of using it to save cycles. curl_multi_select() also allows you to set a timeout but it doesn't seem to help, then again, don't see why people wouldn't use it anyway.
Even when curl_multi_select($mh) does work there's no way to know which of the sockets updated in status or if they've received partial data, completely finished, or just timed out. It's not reliable if you want to remove / add data as soon as things finish. Try calling just example.com or some other website with very little data. curl_multi_select($mh) can send non 0 value a couple of thousand times before finishing. Lazily adding a usleep(25000) or some minimal amount can also help not waste cycles.

If you are using mulit handles and you wish to re-execute any of them (if they timed out or something), then you need to remove the handles from the mulit-handle and then re-add them in order to get them to re-execute. Otherwise cURL will just give you back the same results again without actually retrying.

when you run curl_multi_exec() on the OS X mavericks system you may not get the right return, the scripts may running and running but no return value.
That's because on the OSX system with the php version 5.3.8+, when you call the curl_multi_exec() method before calling the curl_multi_select(), may always return the -1.
So here change a little code to running the curl_multi_exec() successful on OSX below.
<?php
$ch1 = curl_init();
$ch2 = curl_init();
// 设置URL和相应的选项
curl_setopt($ch1, CURLOPT_URL, "http://lxr.php.net");
curl_setopt($ch1, CURLOPT_HEADER, 0);
curl_setopt($ch2, CURLOPT_URL, "http://www.php.net");
curl_setopt($ch2, CURLOPT_HEADER, 0);
// 创建批处理cURL句柄
$mh = curl_multi_init();
// 增加2个句柄
curl_multi_add_handle($mh,$ch1);
curl_multi_add_handle($mh,$ch2);
$active = null;
do {
  $mrc = curl_multi_exec($mh, $active);
} while ($mrc == CURLM_CALL_MULTI_PERFORM);
while ($active && $mrc == CURLM_OK) 
{  
  // add this line
  while (curl_multi_exec($mh, $active) === CURLM_CALL_MULTI_PERFORM);
  if (curl_multi_select($mh) != -1) 
  {  
    do {
      $mrc = curl_multi_exec($mh, $active);
      if ($mrc == CURLM_OK)
      {  
        while($info = curl_multi_info_read($mh))
        {  
          var_dump($info);
        }    
      }  
    } while ($mrc == CURLM_CALL_MULTI_PERFORM);
  }  
}
 //close the handles
curl_multi_remove_handle($mh, $ch1);
curl_multi_remove_handle($mh, $ch2);
curl_multi_close($mh);
?>

This function wait for the last page, can get a configuration array with curl options to made a post, or pass timeouts, etc.
Retun the same array but add "error", and "data".Error is the string destription if something fail, data is the response.
<?php
// author: Daniel G Zylberberg
// date 11 jul 2012 
// $res: array with structure 0=>array("url"=>"blah"),1=>array("url"=>"some url")
// $options (optional): array with curl options (timeout, postfields, etc)
// return the same array that gets, and add "data" to the current row(html content)
// and "error", with the string description in the case that something fail.
function multiCurl($res,$options=""){
    if(count($res)<=0) return False; 
    $handles = array(); 
    if(!$options) // add default options
      $options = array(
        CURLOPT_HEADER=>0,
        CURLOPT_RETURNTRANSFER=>1,
      );
    // add curl options to each handle
    foreach($res as $k=>$row){
      $ch{$k} = curl_init();
      $options[CURLOPT_URL] = $row['url'];
      curl_setopt_array($ch{$k}, $options);
      $handles[$k] = $ch{$k};
    }
    $mh = curl_multi_init(); 
    foreach($handles as $k => $handle){
      curl_multi_add_handle($mh,$handle);
      //echo "<br>adding handle {$k}";
    }
    $running_handles = null;
    //execute the handles
    do {
      $status_cme = curl_multi_exec($mh, $running_handles);
    } while ($cme == CURLM_CALL_MULTI_PERFORM);
    while ($running_handles && $status_cme == CURLM_OK) {
      if (curl_multi_select($mh) != -1) { 
        do {
          $status_cme = curl_multi_exec($mh, $running_handles);
          // echo "<br>''threads'' running = {$running_handles}";
        } while ($status == CURLM_CALL_MULTI_PERFORM);
      }
    }
    foreach($res as $k=>$row){
      $res[$k]['error'] = curl_error($handles[$k]);
      if(!empty($res[$k]['error']))
        $res[$k]['data'] = '';
      else
        $res[$k]['data'] = curl_multi_getcontent( $handles[$k] ); // get results
      // close current handler
      curl_multi_remove_handle($mh, $handles[$k] );
    } 
    curl_multi_close($mh);
    return $res; // return response
} 
$res = array(
    "11"=>array("url"=>"http://localhost/public_html/test/sleep.php?t=1"),
    "13"=>array("url"=>"http://localhost/public_html/test/sleep.php?t=3"),
    "25"=>array("url"=>"this doesn't exist"),
);
print_r( multiCurl($res));
?>
---------- sleep.php -------------------------------------
<?php
sleep($_GET['t']);
echo "sleep for {$_GET['t']} seconds and show this.";
?>

I was testing PHP code provided by dtorop933@gmail.com in curl_multi_exec section of PHP Manual.
The part of the code '$err = curl_error($conn[$i])' should return error message for each cURL session, but it does not.
The function curl_error() works well with the curl_exec(). Is there any other solution for getting session error message with curl_multi_exec() or there is a bug in cURL library.
The script was tested with Windows XP and PHP-5.2.4