Singleton PHP on multiple controllers - php

Question

I created one class (ParseDAO.php) and made it singleton with this method:
public static function getInstance(){
if (self::$instance == null) {
self::$instance = new self();
}
return self::$instance;
}
Then I created 2 controllers. One to login stuff (LoginController.php) and another do dashboard stuff (DashboardController.php)
In LoginController.php I use this code and it works perfectly:
$instance = ParseDAO::getInstance();
$loginResponse = $instance->loginParse($request->get('userName'), $request->get('password'));
if($loginResponse == true){
return redirect()->route('dashboard');
}
else {
return view('login.erroLogin');
}
At DashboardController I have this code:
$instance = ParseDAO::getInstance();
$userId = $instance->getUserId();
This second line just returns the objectId form parse. If I put this line on loginController.php it returns the correct Id, but at DashboardController.php (where I need this data) nothing returns.
It's like another instance was created even using singleton.
Anybody knows how to solve this problem?
Follow the code of loginParse and getUserId:
/**
* Method login
*/
public function loginParse($username, $password){
if($username != null && $password != null){
try {
self::$user = ParseUser::logIn($username, $password);
return true;
}catch (ParseException $error){
return false;
}
}
else{
return false;
}
}
/**
* #return getUserId
*/
public function getUserId(){
return self::$user->getObjectId();
}
And this is the constructor code (with the true keys):
public function __construct()
{
ParseClient::initialize('xxx','xxx','xxx');
self::$user = new ParseUser();
}

Answer 1

Singletons allow for code from a single execution to use the same instance. On every execution (page load), a new instance is created. Every call to ParseDAO::getInstance() will return the same instance, but only within that execution context.
Without seeing the code in loginParse and getUserId, what is most likely occurring is that you are storing information in the ParseDAO class. That information would be kept during the same execution context, but would disappear on the next execution (because it's a new instance).
You'll have to use Sessions to persist information across multiple executions.

Answer 2

Laravel's Service Container offers a quick and easy way to bind a class as a singleton without the need to implement that pattern yourself. So you can use this to register you singleton with the service container:
app()->bind('ParseDAO', function ($app) {
return new ParseDAO;
});
And then you can use this to access that instance:
$instance = app('ParseDAO');
That will make sure you always get the same instance. You can read more about singletons and the Laravel Service container in the Laravel Documentation.