(1) The data type recognized by PHP by default is the application/x-www.form-urlencoded standard data type.
(2) Use Content-Type=text/xml type to submit the content of an xml document to the php server, The type is text The content of /xml cannot be parsed into the $_POST array, so the prototype is retained and received by $GLOBALS['HTTP_RAW_POST_DATA'].
(3) php://input allows reading the original data of POST, cannot be used for enctype="multipart/form- data".