If you send an array in POSTFIELDS, it will be posted as multipart/form-data. I just tried your script and I can get the parameters in $_POST.
Looks like either your server is too old or not configured to support this encoding.
Here is the wire trace,
POST /test HTTP/1.1^M
Host: localhost^M
Accept: */*^M
Content-Length: 243^M
Expect: 100-continue^M
Content-Type: multipart/form-data; boundary=----------------------------b05745ba31db^M
^M
HTTP/1.1 100 Continue^M
^M
------------------------------b05745ba31db^M
Content-Disposition: form-data; name="name"^M
^M
Ross^M
------------------------------b05745ba31db^M
Content-Disposition: form-data; name="php_master"^M
^M
1^M
------------------------------b05745ba31db--^M
HTTP/1.1 200 OK^M
Date: Wed, 02 Jun 2010 20:37:57 GMT^M
Server: Apache/2.2.14 (Unix) mod_ssl/2.2.14 OpenSSL/0.9.7l DAV/2 PHP/5.2.12^M
X-Powered-By: PHP/5.2.12^M
Set-Cookie: ZDEDebuggerPresent=php,phtml,php3; path=/^M
Transfer-Encoding: chunked^M
Content-Type: text/html^M