Delete File Attachment with API_EditRecord

Because someone else might come along looking for this: here's the XML version:

<qdbapi>
<udata>mydata</udata>
   <ticket>auth_ticket</ticket>
   <apptoken>app_token</apptoken>
     <rid>[record_id]</rid>
  <field fid="[field_id]" filename="delete"></field>
</qdbapi>

I also added it to my copy of the PHP API wrapper as a modification of API_Edit:

public function delete_file($rid, $fid) {
  if($this->xml) {
    $xml_packet = new SimpleXMLElement('<qdbapi></qdbapi>');
    $xml_packet->addChild('rid',$rid);
    $xml_packet->addChild('field','');
    $xml_packet->field[0]->addAttribute('fid',$fid);
    $xml_packet->field[0]->addAttribute('filename','delete');

    if ($this->app_token)
      $xml_packet->addChild('apptoken', $this->app_token);
    $xml_packet->addChild('ticket',$this->ticket);
    $xml_packet = $xml_packet->asXML();
    $response = $this->transmit($xml_packet, 'API_EditRecord');
  }
  if($response) {
    return $response;
  }
  return false;
}