title: How to customise JQuery Filedrop to send dynamic post data variables?
body: <p>I'm using the excellent Jquery-Filedrop [weixiyen] used by tutorialzine and I'm stuck on a problem trying to send dynamic POST variables, explained as follows:</p>
  
  <p>I have an html form select drop-down (photo_tab_index) where user can choose a slideshow number (say 1-5) and then a dropbox canvas where the user drops their photos onto to upload to the web server.</p>
  
  <p>In the filedrop javascript I have the following:</p>
  
  <pre><code>$(function(){
    var dropbox = $('#dropbox'),
    message = $('.message', dropbox);
  
    var slideshow = document.getElementById('photo_tab_index').value;
  
    dropbox.filedrop({
      // The name of the $_FILES entry:
      paramname:'pic',
      data: {
        param1: slideshow,           // send POST variables
      },
      ...
  
      // Called before each upload is started
      beforeEach: function(file){
        if(!file.type.match(/^image\//)){
          alert('Only images are allowed!');
          return false;
        }
      },
      ...
  </code></pre>
  
  <p>The problem I have is that the javascript reads the value of the photo_tab_index when it renders the page (and hence are always sent as "1") but what I really want is for it to read the slideshow dropdown value at the point that photos are dropped on the drop box. In my limited JQuery knowledge I have a feeling that I want to be updating the dropbox.filedata "data: param1" field in the beforeEach: function but I'm not sure how I would reference it?</p>