According to MDN XForms has long been obsolete.
» XForms 定义了一种传统 web 表单的变种，它可以用于更多的平台和浏览器，甚至非传统的媒体例如 PDF 文档。
XFroms 的第一个关键区别是表单怎样发送到客户端。» XForms for HTML Authors 包含有怎样创建 XForms 的详细说明。本节只看一个简单例子。
Example #1 一个简单的 XForms 搜索表单
<h:html xmlns:h="http://www.w3.org/1999/xhtml"
xmlns="http://www.w3.org/2002/xforms">
<h:head>
<h:title>Search</h:title>
<model>
<submission action="http://example.com/search"
method="post" xml:id="s"/>
</model>
</h:head>
<h:body>
<h:p>
<input ref="q"><label>Find</label></input>
<submit submission="s"><label>Go</label></submit>
</h:p>
</h:body>
</h:html>
上面的表单显示一个文本输入框（命名为
q）和一个提交按钮。当点击提交按钮，表单将被发送到
action 所指示的页面。
下面是从 web 应用端的角度看上去的区别。在普通的
HTML 表单中，数据发送格式是
application/x-www-form-urlencoded，在
XForms 的世界中，该信息是以 XML 格式数据发送的。
如果选择使用 XForms，那么数据为 XML，这种情况下，在 $HTTP_RAW_POST_DATA 中包含了由浏览器产生的 XML 文档，可以将其传递给所偏好的 XSLT 引擎或者文档解析器。
如果对格式不感兴趣，只想让数据进入到传统的
$_POST 变量中，可以指示客户端浏览器将其以
application/x-www-form-urlencoded
格式发送，只要将 method 属性改成
urlencoded-post 即可。
Example #2 使用 XForm 来产生 $_POST
<h:html xmlns:h="http://www.w3.org/1999/xhtml"
xmlns="http://www.w3.org/2002/xforms">
<h:head>
<h:title>Search</h:title>
<model>
<submission action="http://example.com/search"
method="urlencoded-post" xml:id="s"/>
</model>
</h:head>
<h:body>
<h:p>
<input ref="q"><label>Find</label></input>
<submit submission="s"><label>Go</label></submit>
</h:p>
</h:body>
</h:html>
Note: 在写本文档时，许多浏览器还不支持 XForms。如果上面例子失败请检查自己的浏览器版本。
According to MDN XForms has long been obsolete.
"php://stdin" doesn't exist in my PHP version. I use the following code block instead :
<?php
if (!isset($HTTP_RAW_POST_DATA))
$HTTP_RAW_POST_DATA = file_get_contents("php://input");
?>
FireFox has an XForms plugin that works with the latest nightly builds. Check out http://www.mozilla.org/projects/xforms/ for more info. For IE support, there's an ActiveX control from Novell (http://developer.novell.com/xforms/) and one from x-port.net (http://www.formsplayer.com/).
There's also a JavaScript-based one coming out called FormFaces which looks very promising, especially since there are no plugins required and it works in IE, FF, and Opera: http://www.formfaces.com/
Since HTTP_RAW_POST_DATA requires a configuration to be generated and is not enabled as a default value, you will probably have to use the PHP STDIN stream to get the raw data. It's probably better to use this method as the raw data will not be generated every time, even when not needed.
<?php
$fp = fopen( "php://stdin", "r" );
$data = '';
while( !feof( $fp ) )
$data .= fgets( $fp );
fclose( $fp );
?>