怎么用cookie防止用户的灌水回复

header("content-type:text/html;charset:utf-8;");
/*
chId    21202
content    mmmmmmmmm
docId    11160676
docName    吴卓羲女友张馨予家中大尺度内衣自拍照火辣曝光
docUrl    http://yue.ifeng.com/y/detail_2011_12/07/11160676_0.shtml
*/
  $url = "http://comment.ifeng.com/post.php";
   //$url = "http://localhost/php/index.php";
  $data = array(
    'content'=>'xxxxxxxxxxoooooooooooo',
    'docId'=>11160676,
    'docName'=>'吴卓羲女友张馨予家中大尺度内衣自拍照火辣曝光',
    'docUrl'=>'http://yue.ifeng.com/y/detail_2011_12/07/11160676_0.shtml',
    'chId'=>21202
);
 
$ret = http_post($url,$data);
var_dump($ret);

function http_post($url, $data)
 {
     $ch = curl_init();        
     curl_setopt($ch, CURLOPT_HEADER,1);
     curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    
     curl_setopt($ch, CURLOPT_URL, $url);
     curl_setopt($ch, CURLOPT_POST, 1);
     $data = http_build_query($data);
     curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
     
     curl_setopt($ch, CURLOPT_REFERER, "http://yue.ifeng.com/y/detail_2011_12/07/11160676_0.shtml");
     $cookie = "userid=1323532473389_2814";
     curl_setopt($ch, CURLOPT_COOKIE, $cookie);
     
     $rs = curl_exec($ch);
     curl_close($ch);
     return $rs;
 }