jquery文件上传：如何在提交前更改服务器上传文件

I have been reading the Jquery file upload wiki, but did not come across an example on how to modify the server upload folder on the fly. Is there a working example on how to programmatic modify the php server upload directory?

This is basically off the JQuery Fileupload docs with a little more explanation by me.

//You should bind this to the same object you setup the fileupload on
$('#fileupload').bind('fileuploadsubmit', function (e, data) {
    // The example input, doesn't have to be part of the upload form
    var input = $('#inputWithVariable');

    //Add the new value as a variable called "folder" which will tell you which
    //directory they selected
    data.formData = {folder: input.val()};

    //Optional validation to make sure the input value exists
    if (!data.formData.example) {

     //If the value does not exist, return focus to the input 
     //or maybe select in your case and return false to prevent the upload
      input.focus();
      return false;
    }
});