curl POST -F to php cUrl - php

Question

I'm attempting to POST a local file to an API, it works if I use command line curl but not when I try using php cURL. I set up some variables for the headers and body
$headers = array();
$headers[] = 'Authorization: Passcode '.$passcode;
$headers[] = 'FileType: STD';
$api_url = 'https://url.com';
$field_json = json_encode($field).';type=application/json'
$filepath = realpath('path/file.csv');
$file = new CURLFile($filepath,'text/csv');
curl based on the API's specifications works if I set it as a string and use exec
$cmd = "curl -X POST -H \"$headers[0]\" -H \"$headers[1]\" -F \"field=$field_json\" -F \"filename=#$filepath\" $api_url";
exec($cmd,$result); //This works successfully
but when I attempt to send the POST using the following code with PHP cURL, I get a vague error response 'Unexpected error'
$body = array(
'field' => $field_json,
'filename' => $file
);
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $api_url);
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
curl_setopt($ch, CURLOPT_POST, TRUE);
curl_setopt($ch, CURLOPT_POSTFIELDS, $body);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
//curl_setopt($ch, CURLOPT_SAFE_UPLOAD, FALSE);
$result = curl_exec($ch);
curl_close($ch);
echo json_encode($result);
I'm using PHP 5.5.9 and have tried it using the old way with # and the filepath.