Converting command cURL to PHP - Stuck with passing POSTFIELD data - php

Question

In an attempt to replicate the following cURL:
curl -X POST --header 'Content-Type: multipart/form-data' --header 'Accept: application/json' --header 'Authorization: Bearer XXXXXXXXXX-XXXXXXXXXXX' 'https://XXXXXXXXX.XXX.com/api/v3/assets/76c860cd184ae4adfa105d46135c9b27.json' -F 'name=fileupdate99.pdf' -F 'description=curlviaphp'
The purpose of the call is to update the two fields (name & description) at this specific end point.
I used https://incarnate.github.io/curl-to-php/ to get the bulk of the conversion. However, I appear to be stuck on passing the data.
From what I can tell, it looks like the -F flag is expected (also used to upload files) and I can't make a swap to -d (I tried running call in the command line and -d wasn't accepted).
<?php
$subdomain = "XXXXXXXX";
$name = "fileupdate4.pdf";
$description = "curlviaphp";
$auth = "XXXXXXXXXX-XXXXXXXXXXX";
$asset = "76c860cd184ae4adfa105d46135c9b27";
$ch = curl_init();
$curlurl = "https://" . $subdomain . ".XXX.com/api/v3/assets/" . $asset . ".json' ";
$variables = array(
"name" => $name,
"description" => $description,
);
curl_setopt($ch, CURLOPT_URL, $curlurl);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $variables);
curl_setopt($ch, CURLOPT_POST, 1);
$headers = array();
$headers[] = "Content-Type: multipart/form-data";
$headers[] = "Accept: application/json";
$headers[] = "Authorization: Bearer " . $auth;
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
$result = curl_exec($ch);
if (curl_errno($ch)) {
echo "Error:" . curl_error($ch);
}
curl_close($ch);
echo $result;
?>
When I execute, the code runs and I get a blank page (no return and no change on the receiving end).
What am I missing?