将带有cURL postfields的POST发送到iframe

Question

我正在尝试使用CURL将POST数据发送到网址。这个URL由iframe调用，该iframe位于我的应用程序中。

<iframe frameborder="0" width="950" height="1000" src="/tools/costs"></iframe>


    public function costs()
{   

    $url = "http://someurl.com/tools/costs";


            if($_POST)
            {
                $fields_str = http_build_query($_POST);

                $query = preg_replace('/%5B[0-9]+%5D/simU', '%5B%5D',$fields_str);
                $realstring = str_replace("%5D", "", str_replace("%5B", "", $query));

                // $realstring echo:
                var_carrier=3&var_carrier=5&var_carrier=6&var_service=Demurrage+%2F+Storage&var_service=Detention&var_pod=Ancona&var_pod=Antalya&var_pod=Antwerpen

                $ch = curl_init();
                curl_setopt($ch, CURLOPT_HEADER, 0);
                curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
                curl_setopt($ch, CURLOPT_POST, 1);
                curl_setopt($ch, CURLOPT_POSTFIELDS,$realstring);
                curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
                curl_setopt($ch, CURLOPT_URL, $url);
                $response = curl_exec($ch);
                curl_close($ch);
            }
            else
            {
                $ch = curl_init();
                curl_setopt($ch, CURLOPT_HEADER, 0);
                curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
                curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
                curl_setopt($ch, CURLOPT_URL, $url);
                $response = curl_exec($ch);
                curl_close($ch);
                $fields_str = "";
            }
    echo  $response;
}

但是当我通过cURL POSTFIELDS发送$realstring变量时它是空的 我不知道哇！