Video Uploader via Form

Hi All,

I’m just starting with Transloadit and I’m having trouble uploading a video via a basic form. I can upload a photo no problem:

echo $transloadit->createAssemblyForm(array(
  'params' => array(
    'steps' => array(
      'resize' => array(
        'robot' => '/image/resize',
        'width' => 200,
        'height' => 100,
    'redirect_url' => $redirectUrl

But I’m having trouble with the syntax when trying to change the following code to work with the form:

$response = $transloadit->createAssembly([
  "files" => $files, 
  "params" => [
    "template_id" => "MY_TEMPLATE_ID",

How do I change the above code to work with createAssemblyForm and include the ‘redirect_url’ => $redirectUrl parameter? This is the code I’ve tried:

$redirectUrl = sprintf(
echo $transloadit->createAssemblyForm(array(
  'params' => array(
    'template_id' => 'MY_TEMPLATE_ID'
    'redirect_url' => $redirectUrl,

But I get the error: Error: input[name=params] does not include a redirect_url