PHPcURL并发里的callback那行是什么效能

function rolling_curl($urls, $delay) {

    $queue = curl_multi_init();

    $map = array();

 

    foreach ($urls as $url) {

        $ch = curl_init();

 

        curl_setopt($ch, CURLOPT_URL, $url);

        curl_setopt($ch, CURLOPT_TIMEOUT, 1);

        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);

        curl_setopt($ch, CURLOPT_HEADER, 0);

        curl_setopt($ch, CURLOPT_NOSIGNAL, true);

 

        curl_multi_add_handle($queue, $ch);

        $map[(string) $ch] = $url;

    }

 

    $responses = array();

    do {

        while (($code = curl_multi_exec($queue, $active)) == CURLM_CALL_MULTI_PERFORM) ;

 

        if ($code != CURLM_OK) { break; }

 

        // a request was just completed -- find out which one

        while ($done = curl_multi_info_read($queue)) {

 

            // get the info and content returned on the request

            $info = curl_getinfo($done['handle']);

            $error = curl_error($done['handle']);

            $results = callback(curl_multi_getcontent($done['handle']), $delay);

            $responses[$map[(string) $done['handle']]] = compact('info', 'error', 'results');

 

            // remove the curl handle that just completed

            curl_multi_remove_handle($queue, $done['handle']);

            curl_close($done['handle']);