create ticket with attachments amd custom fields from ajax with php

That's right, but I get an error with the code that has an example in github, this is the error:

{"description":"Validation failed","errors":[{"field":"attachments[]","message":"Unexpected/invalid field in request","code":"invalid_field"}]}

and in my code i have this

$filename = $_FILES['file']['name'];

$filedata = $_FILES['file']['tmp_name'];

$filesize = $_FILES['file']['size'];

$custom_fields = array(

"cf_clasificacin" => $clasificacion,

);

$ticket_payload = json_encode(array(

"description" => $descripcion,

"subject" => $asunto,

"email" => $correo,

"priority" => intval($prioridad),

"status" => intval($estado),

"cc_emails" => array("ram@freshdesk.com", "diana@freshdesk.com"),

"custom_fields" => $custom_fields,

"attachments[]" => curl_file_create($filename, $mimetype, $filedata),

));