ajax post data with document upload

i use Uploadifive and edited the script, so data name and email can be send to uploadifive.php But on sending, the input from the forms stays empty in the database. What am i doin'wrong?

    <script type="text/javascript">
    <?php $timestamp = time();?>
    $(function() {
        var voornaam = $("#voornaam").val();
        var achternaam = $("#achternaam").val();
        var email = $("#email").val();
        $('#file_upload').uploadifive({
            'auto'             : false,
            'checkScript'      : 'check-exists.php',
            'formData'         : {
                                   'timestamp' : '<?php echo $timestamp;?>',
                                   'token'     : '<?php echo md5('unique_salt' . $timestamp);?>',
                                   'voornaam' : voornaam,
                                   'achternaam' :achternaam,
                                   'email' : email
                                 },
            'queueID'          : 'queue',
            'uploadScript'     : 'uploadifive.php',
            'onUploadComplete' : function(file, data) { console.log(data); }
        });
    });
</script>