Requête ajax sur Login

Bonjour à tous.

Je lance une requête Ajax pour enregistrer un nouvel utilisateur dans ma bdd. Mais je pense que je dois faire une erreur au niveau de ma requête.

Mon Form de mon register:

<form id="register-form" style="display:none;">
     <div class="modal-body">
           <div id="div-register-msg">
                  <div id="icon-register-msg" class="glyphicon glyphicon-chevron-right"></div>
                  <span id="text-register-msg">Register an account.</span>
           </div>
           <input id="username" class="form-control" type="text" placeholder="Username (type ERROR for error effect)" required>
           <input id="email" class="form-control" type="text" placeholder="E-Mail" required>
           <input id="password" class="form-control" type="password" placeholder="Password" required>         
           <input id="passwordConfirm" class="form-control" type="password" placeholder="ConfirmPassword" required>
     </div>
     <div class="modal-footer">
           <div>
                 <button type="submit" class="btn btn-primary btn-lg btn-block">Register</button>
           </div>
           <div>
                 <button id="register_login_btn" type="button" class="btn btn-link">Log In</button>
                 <button id="register_lost_btn" type="button" class="btn btn-link">Lost Password?</button>
           </div>
     </div>

</form>

Ma requête ajax:

$('#register-form').on ("submit",function(){

                var username = $("#username").val();
                alert(username)
                var email = $("#email").val();
                alert(email)
                var password = $("#password").val();
                alert(password)
                var passwordConfirm = $("#passwordConfirm").val();
                alert(passwordConfirm)

                $.ajax({
                    url: 'index_new.php',
                    data: 'username='+username+'&email='+email+'&password='+password+'&passwordConfirm='+passwordConfirm,
                    type: 'POST',
                    success: function(response){
                        if(response.status != 'success')                            
                        revertFunc()                   
                    },
                    error: function(e){                    
                        revertFunc();
                        alert('Error processing your request: '+e.responseText);
                    }
                });
                alert('OK')
            });

Et mon php:

if(isset($_POST['submit'])){

    //very basic validation
    if(strlen($_POST['username']) < 3){
        $error[] = 'Username is too short.';
    } else {
        $stmt = $db->prepare('SELECT username FROM members WHERE username = :username');
        $stmt->execute(array(':username' => $_POST['username']));
        $row = $stmt->fetch(PDO::FETCH_ASSOC);

        if(!empty($row['username'])){
            $error[] = 'Username provided is already in use.';
        }

    }

    if(strlen($_POST['password']) < 3){
        $error[] = 'Password is too short.';
    }

    if(strlen($_POST['passwordConfirm']) < 3){
        $error[] = 'Confirm password is too short.';
    }

    if($_POST['password'] != $_POST['passwordConfirm']){
        $error[] = 'Passwords do not match.';
    }

    //email validation
    if(!filter_var($_POST['email'], FILTER_VALIDATE_EMAIL)){
        $error[] = 'Please enter a valid email address';
    } else {
        $stmt = $db->prepare('SELECT email FROM members WHERE email = :email');
        $stmt->execute(array(':email' => $_POST['email']));
        $row = $stmt->fetch(PDO::FETCH_ASSOC);

        if(!empty($row['email'])){
            $error[] = 'Email provided is already in use.';
        }

    }

    //if no errors have been created carry on
    if(!isset($error)){

        //hash the password
        $hashedpassword = $user->password_hash($_POST['password'], PASSWORD_BCRYPT);

        //create the activasion code
        $activasion = md5(uniqid(rand(),true));

        try {

            //insert into database with a prepared statement
            $stmt = $db->prepare('INSERT INTO members (username,password,email,active) VALUES (:username, :password, :email, :active)');
            $stmt->execute(array(
                ':username' => $_POST['username'],
                ':password' => $hashedpassword,
                ':email' => $_POST['email'],
                ':active' => $activasion
            ));
            $id = $db->lastInsertId('memberID');

Mon php fonctionne si je met mon formulaire a l'interrieur et que je m'inscrit.

Donc je pense que mon erreur vient de ma requête ajax. J'ai encore du mal a bien maitriser cette requête.

Merci pour votre aide.