将文件提交到网址后获取响应/结果

I'm trying to submit a file to a REST API url and need to get the response/result from this process. I'm trying to send it to another php and display the result but nothing. If it could display in the same php page then even better. How am i suppose to do that?

<?php
session_start();
// Start the session
$responseURL = "http://my-site.com/responseform.php";
$url = 'https://api-to-validate-file.com/api/validate';
$header = array('Content-Type: multipart/form-data','Authorization: apikey=0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f');
$fields = array('filename' => '@' . $_FILES['filename']['tmp_name'][0]);
$token = 'NfxoS9oGjA6MiArPtwg4aR3Cp4ygAbNA2uv6Gg4m';

$resource = curl_init();
curl_setopt($resource, CURLOPT_URL, $url);
curl_setopt($resource, CURLOPT_HTTPHEADER, $header);
curl_setopt($resource, CURLOPT_RETURNTRANSFER, true);
curl_setopt($resource, CURLOPT_POST, true);
curl_setopt($resource, CURLOPT_POSTFIELDS, $fields);
curl_setopt($resource, CURLOPT_COOKIE, 'apiToken=' . $token);
$result = json_decode(curl_exec($resource));
///echo 'The body of the response is ' . $result;
curl_close($resource);
?>

<form method="post" action="index.php" enctype="multipart/form-data">
    <input name="filename" type="file" />
    <input type="submit" value="Upload" />
    <input type="hidden" name="RespURL" value="<?= $responseURL ?>"><br>
</form>