PHP CURL send multidimensional array with $_FILES

Question

Hi there and thanks for reading.

I'm trying to send data to an API in PHP, everything goes fine but mixin multidimensional arrays and files in the request.

Let's say I have this data:

    $data = [
       'option1' => 'Whatever', 
       'my_arr' => [
          'key1' => 'xxx',
          'key2' => 'yyy'
        ],
       'file' => new CURLFile('/image/path/img.jpg', 'image/jpeg', 'img.jpg');
    ];

I send the data with this function:

 protected function fetchUrl($url, $postParams, $headers = null, $method = 'post', $referer = 'https://www.google.com/', $userAgent = 'Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:95.0) Gecko/20100101 Firefox/95.0')
{
    $methodLower = strtolower($method);
    $handler = curl_init();
    curl_setopt($handler, CURLOPT_URL, $url);
    if ($methodLower === 'get')
        curl_setopt($handler, CURLOPT_HTTPGET, true);
    else if ($methodLower === 'post' || $methodLower === 'put') {
        curl_setopt($handler, CURLOPT_CUSTOMREQUEST, strtoupper($method));
        if ($methodLower === 'post')
            curl_setopt($handler, CURLOPT_POST, true);
        curl_setopt($handler, CURLOPT_POSTFIELDS, http_build_query($postParams));
    }

    if (!empty($userAgent))
        curl_setopt($handler, CURLOPT_USERAGENT, $userAgent);

    if ($headers && count($headers) > 0)
        curl_setopt($handler, CURLOPT_HTTPHEADER, $headers);
    curl_setopt($handler, CURLOPT_FOLLOWLOCATION, 1);
    curl_setopt($handler, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($handler, CURLOPT_REFERER, $referer);
    $body = curl_exec($handler);
    $httpCode = curl_getinfo($handler, CURLINFO_HTTP_CODE);

    if (false === $body)
        error_log(sprintf('FETCH URL ERROR, CODE: %d; MSG: %s, URL: %s', $httpCode, curl_error($handler), $url));

    curl_close($handler);
    if (is_string($body))
        return json_decode($body, JSON_OBJECT_AS_ARRAY);

    return $body;
}

If I wrapp my array with http_build_query my files stop being sent as $_FILE and are transformed to a regular array, If I don't, my multidimensional array can't be sent 'cause curl just accept simple arrays.

So how can I send all data toguether?

Thanks in advance.