文件传输到服务器CURL

Trying to upload a file to server using CURL

The query is formed as:

$postdata = array(
'FileToLoad' => "@".$this->file."; filename=\"$this->filename\";",
'fileId' => $this->fileId);

$this->file contains the full path to the file on the server /var/www/site/data/www/site.ru/tmp/file.pdf

Send:

if( $curl = curl_init() ) {
curl_setopt($curl, CURLOPT_URL, $url);
curl_setopt($curl, CURLOPT_RETURNTRANSFER,true);
curl_setopt($curl, CURLOPT_POST, true);
curl_setopt($curl, CURLOPT_POSTFIELDS, $postdata);
 curl_setopt($curl,CURLOPT_ENCODING, '');
curl_setopt($curl, CURLOPT_COOKIE, ".ASPXAUTH=$this->token;");
$out = curl_exec($curl);
curl_close($curl);
}

The request is successful, but data is in $_POST, and I really want to see in $_FILES. Where am I wrong?