如何能同时请求多个网址？

示例代码：
/*

• @purpose: 使用curl并行处理url
• @return: array 每个url获取的数据
• @param: $urls array url列表
• @param: $callback string 需要进行内容处理的回调函数。示例：func(array)
  */

function curl($urls = array(), $callback = '')
{

$response = array();
if (empty($urls)) {
    return $response;
}
$chs = 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($ch, CURLOPT_NOSIGNAL, true);
    curl_multi_add_handle($chs, $ch);
    $map[strval($ch)] = $url;
}
do{
    if (($status = curl_multi_exec($chs, $active)) != CURLM_CALL_MULTI_PERFORM) {
        if ($status != CURLM_OK) { break; } //如果没有准备就绪，就再次调用curl_multi_exec
        while ($done = curl_multi_info_read($chs)) {
            $info = curl_getinfo($done["handle"]);
            $error = curl_error($done["handle"]);
            $result = curl_multi_getcontent($done["handle"]);
            $url = $map[strval($done["handle"])];
            $rtn = compact('info', 'error', 'result', 'url');
            if (trim($callback)) {
                $callback($rtn);
            }
            $response[$url] = $rtn;
            curl_multi_remove_handle($chs, $done['handle']);
            curl_close($done['handle']);
            //如果仍然有未处理完毕的句柄，那么就select
            if ($active > 0) {
                curl_multi_select($chs, 0.5); //此处会导致阻塞大概0.5秒。
            }
        }
    }
}
while($active > 0); //还有句柄处理还在进行中
curl_multi_close($chs);
return $response;

}

//使用方法
function deal($data){

if ($data["error"] == '') {
    echo $data["url"]." -- ".$data["info"]["http_code"]."\n";
} else {
    echo $data["url"]." -- ".$data["error"]."\n";
}

}
$urls = array();
for ($i = 0; $i < 10; $i++) {

$urls[] = 'http://www.baidu.com/s?wd=etao_'.$i;
$urls[] = 'http://www.so.com/s?q=etao_'.$i;
$urls[] = 'http://www.soso.com/q?w=etao_'.$i;

}
curl($urls, "deal");

参考资料 php实现并发处理之curl篇