从HTTP PUT读取数据

我目前正在实现一个RESTful web服务，它使用CodeIgniter和Phil Sturgeon的REST来讨论XML。我现在纠结于如何从HTTP PUT中读取XML。我就是这么做的。

客户端:

$(function(){
    // Bind a click event to the 'ajax' object id
    $("#new_user").click(function(evt){
        // JavaScript needs totake over. So stop the browser from redirecting the page
        evt.preventDefault();
        var str = '<?xml version="1.0" encoding="UTF-8"?><xml><name>'+$("#txtname").val()+'</name><email>'+$("#txtemail").val()+'</email></xml>';
        // Ajax request to get the data
        $.ajax({
            // URL from the link that was clicked on
            url: $(this).attr("href"),
                        type: "put",
                        contentType: "application/xml",
                        processData: false,
                        data: str,
            success: function(data, textStatus, jqXHR){
                //alert('Successful AJAX request!');
                                   //var items = parseXml(data);
                                   //printXml(items);
            },
            // Failed to load request. This could be caused by any number of problems like server issues, bad links, etc.
            error: function(jqXHR, textStatus, errorThrown){
                alert('Oh no! A problem with the Ajax request!');
            }
        });
    });
});

服务器端:

public function users_put(){
    $input = file_get_contents('php://input');
    print_r($input);
}

它什么也没打印出来。以上JavaScript代码和函数在HTTP POST中运行良好。