How to send empty filename - was: curl with basic authorization and multipart/form-data

Sorry for my previous post, it was my mistake. But I have second question. I am trying to send form over curl, where are many fields and all have to be present. And two fields are input type=file, but I need it to be empty value. I simply need this: Content-Disposition: form-data; name=" text_file"; filename="" Content-Type: application/octet-stream How can I manage it? If I use: $postdata["text_file"] = '@;type=application/octet-stream'; Nothing hapens. I must be existed file or curl do nothing. Thank you for advice. Radek