$_SESSION['exist']=true even if not set - php

Question

i'm about to update my website and since i have offshored some code it want work anymore...
My problem now is, that i want to update the stats, when a new user visits my site but it doesn't go into the if, because the $_SESSION['exist'] is just true, even if not stated.
My code looks like this:
<?php
session_start();
if(!isset($_SESSION['exist'])){ //it doesn't go in this if
$_SESSION['exist'] = true;
$today = date("Y/m/d");
require(__DIR__ . '/./functions/select/stats/daily_view.php');
$dailyview = selectDailyView();
echo $dailyview['date'];
if($dailyview['date'] != $today){
//start COPY
$dv = selectDailyView();
require_once(__DIR__ . '/./functions/insert/stats/dailyview.php');
insertDailyView($dv[0]['date'], $dv[0]['dailyview']);
//end COPY
require_once(__DIR__ . '/./functions/update/stats/reset_daily_view.php');
updateResetDailyviewDate($today);
}
require_once(__DIR__ . '/./functions/update/stats/stats.php');
updateStat('index');
require_once(__DIR__ . '/./functions/update/stats/dailyview.php');
updateDailyView();
}
?>
So i tried to comment out everything except the session_start(); and to see whats stored in the $_SESSION i wrote a var_dump($_SESSION); and it says
array(1){["exist"]=>bool(true)}
I tried to clear the cache, unset the $_SESSION, destroy the session... Nothing worked. With unset($_SESSION); the output is NULL, but when i delete that line and reload the page the output still says
array(1){["exist"]=>bool(true)}
Do you have any idea?

Answer 1

You have to unset it :
unset($_SESSION['exist']);