PHP session not logging out / unset - php

Question

I know this question has many duplicates, but I tried several of them and none of those have been answered.
Here is my code for logout.php:
<?php
session_start();
require './codefiles/dbhelper.php';
$dbh = new DbHelper();
$dbh->Execute('UPDATE surveyors SET LoggedIn=\'0\', SessionID=\'\' WHERE Username=\''.$_SESSION['username'].'\'');
session_unset();
session_abort();
session_destroy();
$_SESSION = array();
unset($_SESSION['username']);
unset($dbh);
header('location:index.php');
?>
But the session variables are just too "stubborn" to be removed. Neither session values are being cleared not the session variables are being removed. Object $dbh is being unset but not $_SESSION['username'];
Another unrelated problem, despite I am setting the LoggedIn = 0, in my SQL query, it just stays as 1 in database. LoggedIn field is of type 'bit'. SessionID field is set to blank though.
Any solutions please?
EDIT:
Removed echo $dbh->error as it was unnecessary.
EDIT 2:
Added session_destroy() as suggested by Hossam Magdy.

Answer 1

<?php
include 'codefiles/dbhelper.php';
if(!isset($_SESSION['id']))
{
header ("Location: login_form.php");
}
else
{
session_destroy();
die('You have been logged out.<meta http-equiv="refresh" content="0;url=login_form.php">');
}
?>
This is basically the "Logout" structure.

Answer 2

I don't know why, but the code for destroying the sessions was somehow not working in logout.php. It worked in index.php and other files, but will all sorts of unpredictable behavior.
Found a workaround to circumvent the problem. The logout.php has code as below:
<?php
session_start();
$_SESSION['logout'] = TRUE;
header('location:index.php');
?>
And add this code to index.php:
# Implement logout functionality
<?php
session_start();
if(isset($_SESSION['logout']) && $_SESSION['logout'] == TRUE){
foreach($_SESSION as $var => $value){
unset($_SESSION[$var]);
}
session_destroy();
session_unset();
}
?>
It may not be a standardized solution, but the code works for me every time, with no unpredictable behavior.
Thanks everyone for sharing their ideas.

Answer 3

Try this
<?php
session_start();
require './codefiles/dbhelper.php';
$dbh = new DbHelper();
$dbh->Execute('UPDATE surveyors SET LoggedIn=\'0\', SessionID=\'\' WHERE Username=\''.$_SESSION['username'].'\'');
echo session_status() . '<br />';
session_unset();
session_destroy();
echo session_status();
// header('location:index.php');
Let's see what session_status() says.
But on my projects unset && destroy work.