form_data?

Determine whether the request body contains form-data by checking the request Content-Type for one of the media-types: application/x-www-form-urlencoded or multipart/form-data. The list of form-data media types can be modified through the FORM_DATA_MEDIA_TYPES array.

A request body is not assumed to contain form-data when no Content-Type header is provided and the request_method is POST.