Error sending form on a twitter bootstrap to php mysql using ajax

Am trying to submit data using modal bootstrap but i can’t get it to work. The page will contain more than one modal to enable user to easily update their details.Here the code.

    <div class="modal fade" id="overview-modal" role="dialog">
                <div class="modal-dialog">
                    <!-- Modal content-->
                    <div class="modal-content">
                        <div class="modal-header">
                            <button type="button" class="close" data-dismiss="modal">&times;</button>
                            <h4 class="modal-title">Overview</h4>
                        </div>
                        <form  id="overview_form" action="neuro/update_profile.php" class="form-horizontal" >
                            <div class="modal-body">
                                <div class="form-group">
                                    <label for="inputEmail3" class="col-sm-2 control-label">Overview</label>
                                    <div class="col-sm-10">
                                        <textarea class="form-control" id="overview_input" cols="20" rows="10" name="overview_textarea">

                                        </textarea>
<input type="hidden" name="url"/>
                                    </div>
                                </div>

                                <div class="form-group">

                                </div>
                            </div>
                            <div class="modal-footer">
                                <div class="btn-group">

                                    <input type="submit" id="save" class="btn btn-success" value="Save"/>
                                    <button type="button" class="btn btn-default" data-dismiss="modal">Close</button> 
                                </div>

                            </div>
                        </form>
                    </div>
                </div>
            </div>

This is the javascript that will handle the form submission to the php file

<script>
        $(document).ready(function () {


            $("#save").submit(function () {
                var formData = $("form#overview_form").serialize();
                var my_url = "neuro/update_profile.php";
                $.ajax({
                    type: "POST",
                    url: my_url,
                    data: formData ,
                    success: function (msg) {
                        $("#overview-modal").modal('hide');
                    },
                    error: function () {
                        alert("Error encounted");
                    }
                });

               return false;
            });
        });
    </script>

The php is in a folder called neoro/update_profile ,since i will be using more than one modal in the profile page i have decided to append a url on the form attributes so that it can be easily processed in the php

    $profile = new Profile();
$url = $_POST['url'];
if (isset($url)) {
    if ($id == "overview") {

        $overview = $_POST['overview'];
        $profile->save_overview($user_id, $overview);
        return TRUE;
    }
} else {
    header("Location: ./profile.php");
}