官方提供的例子，一次执行多个连接，然后阻塞所有链接完成取内容，整个过程是阻塞的。
<?php
// 创建单个cURL资源
$ch1 = curl_init();
$ch2 = curl_init();
// 设置URL和相应的选项
curl_setopt($ch1, CURLOPT_URL, "https://www.haiyun.me/");
curl_setopt($ch1, CURLOPT_HEADER, 0);
curl_setopt($ch1, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch2, CURLOPT_URL, "https://www.haiyun.me/");
curl_setopt($ch2, CURLOPT_HEADER, 0);
curl_setopt($ch2, CURLOPT_RETURNTRANSFER, 1);
// 创建批处理cURL句柄
$mh = curl_multi_init();
// 增加单个句柄到批处理
curl_multi_add_handle($mh,$ch1);
curl_multi_add_handle($mh,$ch2);
$active = null;
// 执行批处理句柄，循环任务直到全部执行，不等待返回结果
do {
$mrc = curl_multi_exec($mh, $active);
} while ($mrc == CURLM_CALL_MULTI_PERFORM);
//循环判断任务是否执行完成
while ($active && $mrc == CURLM_OK) {
//阻塞等待cURL批处理中的活动连接，失败时返回-1，不等于-1代表还有活动连接
if (curl_multi_select($mh) != -1) {
//有活动连接时继续执行批处理句柄
do {
$mrc = curl_multi_exec($mh, $active);
} while ($mrc == CURLM_CALL_MULTI_PERFORM);
}
}
//获取单个URL返回的内容
var_dump(curl_multi_getcontent($ch1));
// 关闭全部句柄
curl_multi_remove_handle($mh, $ch1);
curl_multi_remove_handle($mh, $ch2);
curl_multi_close($mh);
?>非阻塞实现http://code.google.com/p/rolling-curl/，不过在循环时是根据curl_multi_exec返回的运行状态判断的，大量链接时经常没完成就跳出，修改了下根据循环的队列是否完成来判断。
<?php
$isruning = 1;
do {
//执行句柄内所有连接，包括后来新加入的连接
do {
$execrun = curl_multi_exec($master, $running);
} while ($execrun == CURLM_CALL_MULTI_PERFORM);
//while (($execrun = curl_multi_exec($master, $running)) == CURLM_CALL_MULTI_PERFORM) ;
//if ($execrun != CURLM_OK)
//break;
//有连接返回立即处理，并加入新的连接
while ($done = curl_multi_info_read($master)) {
//获取返回的信息
$info = curl_getinfo($done['handle']);
$output = curl_multi_getcontent($done['handle']);
//发送返回信息到回调函数
$callback = $this->callback;
if (is_callable($callback)) {
//获取返回信息的句柄
$key = (string) $done['handle'];
//根据请求映射是哪个请求返回的信息
$request = $this->requests[$this->requestMap[$key]];
unset($this->requestMap[$key]);
call_user_func($callback, $output, $info, $request);
}
//判断队列内的连接是否用完
if ($i < sizeof($this->requests) && isset($this->requests[$i]) && $i < count($this->requests)) {
$ch = curl_init();
$options = $this->get_options($this->requests[$i]);
curl_setopt_array($ch, $options);
//增加新的连接
curl_multi_add_handle($master, $ch);
//添加到request Maps，用于返回信息时根据handle找到相应连接
$key = (string) $ch;
$this->requestMap[$key] = $i;
$i++;
}
else {
//循环结束
$isruning = 0;
}
//删除完成的句柄
curl_multi_remove_handle($master, $done['handle']);
}
// Block for data in / output; error handling is done by curl_multi_exec
if ($running)
curl_multi_select($master, $this->timeout);
} while ($isruning);
?>