Sending multipart/form-data request with PECL.

I am trying to submit a request to an HTTP server with multipart/form-data encoded data. I'm using PECL's HttpRequest (although I'm open to alternatives). I am using PHP5. I noticed that if you call addPostFile to add a file, PECL will send the file, and all other post parameters, with multipart/form-data encoding, so I know PECL has the capability to do it. If you simply call addPostFields but never call addPostFile, it uses standard post encoding. Is there a way to force PECL to use multipart/form-data encoding for all post fields added with addPostFields, even when you are not calling addPostFile to add a file? If not, is there another good way to encode multipart data with PHP? Thanks! Jason