<?php
public function createAction(){
    require "Views/Users/new.php";  

    // initialise $validation and $errors
    $validation = true;
    $errors = [];

    if (empty($_POST["email"])) {
        $validation = false;
        array_push($errors, "Field 'email' is required.");
    } elseif (!filter_var($_POST["email"],FILTER_VALIDATE_EMAIL)) {
        $validation = false;
        array_push($errors, "Field'email' invalid format.");
    }
    if ($validation) {
        $user = new Users();
        $user->email = $_POST["email"];
        $status = Users::insert($user);
    }

    // this probably should be !$validation
    if (!$validation) {

        // you set $_SESSION["users-create-errors"]
        // and then if its set which it of course will be 
        // you destroy it?????

        //$_SESSION["users-create-errors"] = $errors;
        //if (array_key_exists("users-create-errors", $_SESSION)) {
            //unset($_SESSION["users-create-errors"]);
        //}

        // just set it to a new value which will overwrite anything
        // that is left in there. But this shoudl be cleaned out
        // when the errors have been reported to the user
        $_SESSION["users-create-errors"] = $errors;

}