php通过curl来模似post提交

function curl($url,$post='') {
   $cookiefile = "cookie.txt";
   $timeout = 30;
   $jump = true;
   $nobody = false;
   $header = false;
   $user_agent = 'Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv:1.9.0.8) Gecko/2009032609 Firefox/3.0.8';
   $moreopt = false;

   $ch = curl_init($url);
   if($post){
    $mainopt=array(
     CURLOPT_CONNECTTIMEOUT=>$timeout,
     CURLOPT_COOKIEFILE=>$cookiefile,
     CURLOPT_COOKIEJAR=>$cookiefile,
     CURLOPT_AUTOREFERER=>$jump,//自动跳转
     CURLOPT_FOLLOWLOCATION=>$jump,//自动跳转
     CURLOPT_USERAGENT=>$user_agent,//设定浏览器
     CURLOPT_RETURNTRANSFER=>true,//返回字符串
     CURLOPT_SSL_VERIFYPEER=>false,
     CURLOPT_POST=>1,
     CURLOPT_POSTFIELDS=>$post,
     CURLOPT_HEADER=>$header,
     CURLOPT_NOBODY=>$nobody
    );
    curl_setopt_array($ch, $mainopt);
   }
   else{
    $mainopt=array(
     CURLOPT_CONNECTTIMEOUT=>$timeout,
     CURLOPT_COOKIEFILE=>$cookiefile,
     CURLOPT_COOKIEJAR=>$cookiefile,
     CURLOPT_AUTOREFERER=>$jump,//自动跳转
     CURLOPT_FOLLOWLOCATION=>$jump,//自动跳转
     CURLOPT_USERAGENT=>$user_agent,
     CURLOPT_SSL_VERIFYPEER=>false,
     CURLOPT_HEADER=>$header,
     CURLOPT_NOBODY=>$nobody,
     CURLOPT_RETURNTRANSFER=>true
    );
    curl_setopt_array($ch, $mainopt);
   }

   if($moreopt)
   curl_setopt_array($ch,$moreopt);

   $string=curl_exec($ch);
   if(!$string){
    return false;
   }

   $curlinfo=curl_getinfo($ch);
   //unlink($cookiefile);
   curl_close($ch);
   return $string;
}