getting results from a site using curl - php

Question

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;
?>

Answer 1

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.