Store value of session key then unset? - php

Question

I'm trying to imitate the behavior of flash messages in native PHP, for one-time display of error messages.
Displaying the Login page:
public function showLoginAndRegistrationPage()
{
$session = new Session();
$data['errors']['login']['account'] = $session->getFormErrorFlashData('login', 'account');
$this->viewPresenter->display('basic', 'customer/login-registration', $data, 'Login/Register');
}
Verifying the login details:
public function processLogin()
{
// Some code
$session = new Session();
if($this->formInputFilter->isValid()) {
// Some code
if(true) {
// Some code
} else {
$errors = array(
'account' => 'Account does not exist.'
);
$session->setFormErrorFlashData('login', $errors);
header('Location: /login');
}
} else {
header('Location: /login');
}
}
For setting the error messages:
public function setFormErrorFlashData($form, $errors = array())
{
foreach($errors As $field => $message) {
$_SESSION['errors']["{$form}"]["{$field}"] = $message;
}
}
For getting the error messages stored in the session:
public function getFormErrorFlashData($form, $field)
{
if(isset($_SESSION['errors']["{$form}"]["{$field}"])) {
$message = $_SESSION['errors']["{$form}"]["{$field}"];
unset($_SESSION['errors']["{$form}"]["{$field}"]);
return $message;
}
}
Basically for an invalid attempt, after redirect, it should now display the 'Account does not exist' message, and then when the user refreshes the page, it should no longer be there.
What happens is when I comment out the unset() line in getFormErrorFlashData(), the $_SESSION contains the errors, but of course as expected they do persist even after countless page refreshes.
But when it's not commented out, I get a NULL. It seems that $message is also unset, even after attempting to store in it the value of that session key.
I have a bootstrap file that has the session_start() line, it's loaded for every page so I doubt that's the cause?
UPDATE:
index.php (bootstrap file)
<?php
session_start();
date_default_timezone_set('Asia/Taipei');
require_once 'core/Autoloader.php';
use core\Autoloader As Autoloader;
use core\Router As Router;
use core\Dispatcher As Dispatcher;
spl_autoload_register('core\Autoloader::loadClass');
$request_uri = trim($_SERVER['REQUEST_URI']);
$router = new Router();
$route = $router->handleRequest($request_uri);
if (!$route) {
require_once ('./views/errors/404.php');
} else {
$dispatcher = new Dispatcher($route);
$isDispatched = $dispatcher->dispatch();
if (!$isDispatched) {
echo '<div>' .$route['class'] .'/' . $route['action'] . ' not found </div>';
require_once ('./views/errors/404.php');
}
}

Answer 1

I've found the culprit.
When I traced the request logs, showLoginAndRegistrationPage() was being called twice because I didn't realize I also had a .js file attached in the html file with a submit event handler that gets fired too, thus the double page requests.
I removed the file and now it's working.
Thanks for the help!