怎么样通过PHP使用curl代理实现抓取数据功能？

<?php
define ( 'IS_PROXY', true ); //是否启用代理
function async_get_url($url_array, $wait_usec = 0)
{
 if (!is_array($url_array))
  return false;
 $wait_usec = intval($wait_usec);
 $data = array();
 $handle = array();
 $running = 0;
 $mh = curl_multi_init(); // 开启多线程
 $i = 0;
 foreach($url_array as $url) {
  $ch = curl_init();
  if (IS_PROXY) {
  //以下代码设置代理服务器
  //代理服务器地址http://www.cnproxy.com/proxy1.html !!Hong Kong, China的速度比较好
  curl_setopt ($ch, CURLOPT_PROXY,'110.4.12.170:80' );
  }
  curl_setopt($ch, CURLOPT_URL, $url);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); // return don't print
  curl_setopt($ch, CURLOPT_TIMEOUT, 30); //设置超时时间
  curl_setopt($ch, CURLOPT_USERAGENT, 'Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)');
  curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1); // 302 redirect
  curl_setopt($ch, CURLOPT_MAXREDIRS, 7); //HTTp定向级别
  curl_multi_add_handle($mh, $ch); // 把 curl resource 放进 multi curl handler 里
  $handle[$i++] = $ch;
 }
 /* 执行 */
 do {
  $mrc = curl_multi_exec($mh, $running);
  if ($wait_usec > 0) /* 每个 connect 要间隔多久 */
   usleep($wait_usec); // 250000 = 0.25 sec
 } while ($mrc == CURLM_CALL_MULTI_PERFORM);
 while ($running && $mrc == CURLM_OK) {
  if (curl_multi_select($mh) != -1) {
   do {
    $mrc = curl_multi_exec($mh, $running);
   } while ($mrc == CURLM_CALL_MULTI_PERFORM);
  }
 }
 /* 读取资料 */
 foreach($handle as $i => $ch) {
  $content = curl_multi_getcontent($ch);
  $data[$i] = (curl_errno($ch) == 0) ? $content : false;
 }
 /* 移除 handle*/
 foreach($handle as $ch) {
  curl_multi_remove_handle($mh, $ch);
 }
 curl_multi_close($mh);
 return $data;
}
$urls = array('http://map.baidu.com');
$re = async_get_url($urls);
echo $re[0];
?>