Last updated: Fri, 05 Sep 2008

curl_multi_exec

(PHP 5)

curl_multi_exec — Run the sub-connections of the current cURL handle

Description

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

Processes each of the handles in the stack. This method can be called whether or not a handle needs to read or write data.

Parameters

mh: A cURL multi handle returned by curl_multi_init().
still_running: A reference to a flag to tell whether the operations are still running.

Return Values

A cURL code defined in the cURL Predefined Constants.

Note: This only returns errors regarding the whole multi stack. There might still have occurred problems on individual transfers even when this function returns CURLM_OK.

Examples

Example #1 curl_multi_exec() example

This example will create two cURL handles, add them to a multi handle, and then run them in parallel.


<?php
// create both cURL resources
$ch1 = curl_init();
$ch2 = curl_init();

// set URL and other appropriate options
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);

//create the multiple cURL handle
$mh = curl_multi_init();

//add the two handles
curl_multi_add_handle($mh,$ch1);
curl_multi_add_handle($mh,$ch2);

$active = null;
//execute the handles
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);
    }
}

//close the handles
curl_multi_remove_handle($mh, $ch1);
curl_multi_remove_handle($mh, $ch2);
curl_multi_close($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.

robert dot reichel at boboton dot com
20-Oct-2007 02:54


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

shichuanr at gmail dot com
06-Sep-2007 02:12


For people who have problem running the above example script(Example 425. curl_multi_exec()), you can alter it a little bit to make it work properly by replacing the existing chunk of code with the one below: 



<?php

// create both cURL resources

$ch1 = curl_init();

$ch2 = curl_init();



// set URL and other appropriate options

curl_setopt($ch1, CURLOPT_URL, "http://www.google.com/");

curl_setopt($ch1, CURLOPT_HEADER, 0);

curl_setopt($ch2, CURLOPT_URL, "http://www.php.net/");

curl_setopt($ch2, CURLOPT_HEADER, 0);



//create the multiple cURL handle

$mh = curl_multi_init();



//add the two handles

curl_multi_add_handle($mh,$ch1);

curl_multi_add_handle($mh,$ch2);



$running=null;

//execute the handles

do {

    curl_multi_exec($mh,$running);

} while ($running > 0);

//close the handles

curl_multi_remove_handle($mh,$ch1);

curl_multi_remove_handle($mh,$ch1);

curl_multi_close($mh);



?>

substr("iscampifriese",1,11) dot " at beer dot com"
04-Jul-2007 03:10


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.

add a note

curl_multi_getcontent

curl_multi_close