file.php

    $("#orderForm").submit(function (event) {

            $.ajax({
                type: "POST",
                url: "<?php bloginfo('stylesheet_directory')?>/formvalidate.php",
                /*data: formData,*/
               /* dataType: 'json',*/
                encode: true
            }).done(function (data) {
                alert(data);
            }).fail(function (xhr, status, error) {
                alert("fail "+error.toString());
            });
           event.preventDefault();

        });

        // new WOW().init();
    });

formvalidate.php

<?php
$name = $_POST["oName"];
echo $name;
?>