retrieve POST body?

Greetings, Is there any way to retrieve the POST message body when a form is submitted to a PHP script using multipart/form-data? I can't use just the $_POST[] and $_FILES[] arrays because I need to calculate the hash of an exact bit-accurate copy of the original POST body for data verification. (HTTP digest authentication with qop="auth-int".) Submitting the form using application/x-www-form-urlencoded is not an option either because the PHP script has to be able to handle forms with file uploads.