Determine PHP Session startet
26.09.2016 - Manuel Wohlers
<?php
// PHP versions >= 5.4.0
if (session_status() == PHP_SESSION_NONE) {
session_start();
}
// PHP versions < 5.4.0
if(session_id() == '') {
session_start();
}
Quelle: http://www.php.net/manual/en/function.session-status.php