getting results from a site using curl

I have been trying to post some variables to a site using POST method, using curl to get some results. I am posting to this link.

http://www.rasta.pk/Lhr/Lhr_Traffic.aspx

At this page you will see a drop down menu .. onchange some values are returned in "Yellow" colored table.

I have monitored this site and trying to get those results by making a post request to that link. But, I am getting "Bad Header" error. I have tried changing things but ubable to find a solution.

Here is my code:

 "Canal Bank Rd",
       "ScriptManager1 " => "UpdatePanelDDLRoads|DropDownRoads",
       "__EVENTARGUMENT" => "",
       "__EVENTTARGET" => "DropDownRoads" 
   );
   $ch = curl_init();
   curl_setopt($ch, CURLOPT_URL, $url);
   curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
   curl_setopt($ch, CURLOPT_HTTPHEADER, $headerz);
   curl_setopt($ch, CURLOPT_HEADER, 0);
   curl_setopt($ch, CURLOPT_POST, 1);
   curl_setopt($ch, CURLOPT_POSTFIELDS, $post_data);
   curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 0);
   curl_setopt($ch, CURLOPT_REFERER, "http://www.rasta.pk/Lhr/Lhr_Traffic.aspx");
   curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
   $output = curl_exec($ch);
   curl_close($ch);
   echo $output;
   开发者_开发百科?>

There's too little details presented for us to know for sure.

A guess is that you're doing the wrong kind of post, since when you pass in a hash array to CURLOPT_POSTFIELDS it will do a multipart formpost which might not be what the server expects. Pass in a string instead to make a "normal" POST.

If that is not enough, use LiveHTTPHeaders or similar in a browser to figure out exactly what is sent in a "manual" session and then you make sure that your curl program mimics that operation as closely as possible.