cURL发布表单并返回结果

i'm trying to get result from this site by using cURL. its just return white page not with the download link.what's wrong with my code?

This's my codes

<?php
// Define URL where the form resides
$form_url = "http://www.tusfiles.net/83gjiu9h49nw";

// This is the data to POST to the form. The KEY of the array is the name of the field. The value is the value posted.
$data_to_post = array();
$data_to_post['op'] = 'download2';
$data_to_post['id'] = '83gjiu9h49nw';
$data_to_post['rand'] = 'utpaxiqp4ocv6krspq5geslurstt7z3bmvt5eqa';
$data_to_post['referer'] = '';
$data_to_post['method_free'] = '';
$data_to_post['method_premium'] = '';
$data_to_post['submit'] = 'Direct download link';

// Initialize cURL
$curl = curl_init();

// Set the options

curl_setopt($curl,CURLOPT_USERAGENT,'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.13) Gecko/20080311 Firefox/2.0.0.13');

curl_setopt($curl,CURLOPT_URL, $form_url);

// This sets the number of fields to post
curl_setopt($curl,CURLOPT_POST, sizeof($data_to_post));

// This is the fields to post in the form of an array.
curl_setopt($curl,CURLOPT_POSTFIELDS, $data_to_post);

//execute the post
$result = curl_exec($curl);

//close the connection
curl_close($curl);

?>

Thx

You may need to url encode the data in the body of your POST request. So instead of:

$data_to_post['submit'] = 'Direct download link';

You'd have:

$data_to_post['submit'] = urlencode('Direct download link');