try like this
$(':submit').click(function(e){
$("#myform").validationEngine(
{
onValidationComplete: function(form, status){
if(status == true){
submitMessage();
}
});
});
function submitMessage()
{
var formData = new FormData($('#myform')[0]);
$.ajax({
url: 'upload.php',
type: 'POST',
xhr: ...
beforeSend: beforeSendHandler,
success: completeHandler,
error: errorHandler,
data: formData,
cache: false,
contentType: false,
processData: false
});
}