php delete session

1session_destroy(); // To delete whole session
2// OR
3unset($_SESSION['myVar']); // To delete a session var

1<?php 
2 session_start(); // start session
3 session_destroy();  // Delete whole session
4// OR
5unset($_SESSION['username']); // delete any specific session only
6?>

1<?php
2   unset($_SESSION['counter']);
3?>

1// Create a session variable called something like this after you start the session:
2$_SESSION['user_start'] = time();
3 
4// Then when they get to submitting the payment, just check whether they're within the 5 minute window
5if (time() - $_SESSION['user_start'] < 300) { // 300 seconds = 5 minutes
6    // they're within the 5 minutes so save the details to the database
7} else {
8    // sorry, you're out of time
9   unset($_SESSION['user_start']); // and unset any other session vars for this task
10}

1<?php
2// Destroy the currently active session.
3session_destroy();
4?>

1
2All of a sudden neither session_destroy() nor $_SESSION=[] were sufficient to log out. I found the next to work:
3<?php
4setcookie(session_name(), session_id(), 1); // to expire the session
5$_SESSION = [];
6?>
7
8