I wrote a mail compose php script and run it in phped, but can not get the $_POST values when set the enctype property of the form to "multipart/form-data". For uploading attachments, I must do that. And the script seems work well out of phped. Any thing wrong with phped?

no. Nothing wrong with phped.
It's SRV (embedded server) has limited functionality.
Please use Apache for your development with phped.