Send value on onsubmit

I want to send document.getEleme开发者_开发问答ntById('source').value onsubmit. How can i send? thanks this value document.getElementById('source').value working fine. But I want to call this on submit. Because some time user could change the value.

new AjaxUpload(btnUpload, {
        action: 'upload-file.php?source='+document.getElementById('source').value+'&destination='+document.getElementById('destination').value+'&subjectarea='+document.getElementById('subjectarea').value+'&order_id='+document.getElementById('order_id').value,
        name: 'uploadfile',
        onSubmit: function(file, ext,source){
             if (! (ext && /^(txt|pdf|doc|docx|pptx|ppt|xlsx|xls)$/.test(ext))){ 
                // extension is not allowed 
                status.text('Only TXT, PDF, PPTX, PPT, XLS, XLSX, DOC or DOCX files are allowed');
                return false;
            }
            ;
            status.text('Uploading...');
        }

you should put it in an input type value and then in the server - use REquest["id"] to get the val

$.ajax({
    url:upload-file.php',
    data:{source:$('#source').val(),destination:$('destination').val(),subjectarea:$('#subjectarea').val(),order_id:$('#order_id').val()},
    type:'post',
    dataType:'text',
    success:function(msg){
        $('#div').html(msg);
    },
    error:function(){
        // handle your error
    }
});

here "data" is used to send the variable to requested file. you can get these variable in your requested file by using $_POST[] OR $_REQUEST[] variable.

So name of the variable would be $_POST['source'], $_POST['destination'] and so on