使用preg_match_all和curl来捕获字段的值

Question

I am trying to do an automatic post using curl, but the problem is that there is a hidden field that changes its value every time the page is loaded. So I used preg_match_all to capture this value and pass it to the post. The fact is preg_match_all is not returning anything.

This is the piece of code I'm using:

  $ch = curl_init();
  curl_setopt($ch,CURLOPT_URL,'http://www.blidoo.es/pub/');
  curl_setopt($ch,CURLOPT_USERAGENT,'Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)');
  curl_setopt($ch,CURLOPT_HTTPHEADER,array("Accept-Language: es-es,en"));
  curl_setopt($ch,CURLOPT_HEADER,false);
  curl_setopt($ch,CURLOPT_RETURNTRANSFER,true);
  curl_setopt($ch,CURLOPT_FOLLOWLOCATION,true);
  curl_setopt($ch,CURLOPT_PROXYTYPE,'HTTP');
  curl_setopt($ch,CURLOPT_PROXYPORT,'5677');
  curl_setopt($ch,CURLOPT_PROXY,'192.168.11.16');
  curl_setopt($ch,CURLOPT_PROXYUSERPWD,'daemon@AgentOrange.1989');


  $result = curl_exec($ch);
  $rerror = curl_error($ch);
  curl_close($ch);

  preg_match_all("(<input type=\"hidden\" name=\"publicar[_csrf_token]\" value=\"(.*)\" id=\"publicar__csrf_token\" />)siU",$result,$matches1);
  $return = trim($matches1[1][0]);

I have checked the $result and the string is there. What am I doing wrong?