session_destroy(); // To delete whole session
// OR
unset($_SESSION['myVar']); // To delete a session var

<?php session_start(); // start session session_destroy(); // Delete whole session
// OR
unset($_SESSION['username']); // delete any specific session only
?>

<?php
// Destroy the currently active session.
session_destroy();
?>

// Create a session variable called something like this after you start the session:
$_SESSION['user_start'] = time();
// Then when they get to submitting the payment, just check whether they're within the 5 minute window
if (time() - $_SESSION['user_start'] < 300) { // 300 seconds = 5 minutes // they're within the 5 minutes so save the details to the database
} else { // sorry, you're out of time unset($_SESSION['user_start']); // and unset any other session vars for this task
}

<?php
// Initialize the session.
// If you are using session_name("something"), don't forget it now!
session_start();
// Unset all of the session variables.
$_SESSION = array();
// If it's desired to kill the session, also delete the session cookie.
// Note: This will destroy the session, and not just the session data!
if (ini_get("session.use_cookies")) {
    $params = session_get_cookie_params();
    setcookie(session_name(), '', time() - 42000,
        $params["path"], $params["domain"],
        $params["secure"], $params["httponly"]
    );
}
// Finally, destroy the session.
session_destroy();
?>

<?php
// Initialize the session.
// If you are using session_name("something"), don't forget it now!
session_start();
// Unset all of the session variables.
$_SESSION = array();
// If it's desired to kill the session, also delete the session cookie.
// Note: This will destroy the session, and not just the session data!
if (ini_get("session.use_cookies")) { $params = session_get_cookie_params(); setcookie(session_name(), '', time() - 42000, $params["path"], $params["domain"], $params["secure"], $params["httponly"] );
}
// Finally, destroy the session.
session_destroy();
?>

<?php
session_start();
// 2 hours in seconds
$inactive = 7200;
$session_life = time() - $_session['testing'];
if($session_life > $inactive)
{ session_destroy();
}
$_session['testing']=time(); echo $_SESSION['testing']; //prints NOTHING? ?>

req.session.destroy();