Is there a way to check if the current page was opened with SSL? For example, I want my login page (login.php) to check if it was accessed using SSL (https://mywebserver.com
You should be able to check that $_SERVER['HTTPS'] is set, e.g.:
$_SERVER['HTTPS']
if (empty($_SERVER['HTTPS'])) { header('Location: https://mywebserver.com/login.php'); exit; }