Você está procurando por
CURDATE()
:$db->query("SELECT * FROM events WHERE event_date >= CURDATE()");
Ou:
$db->query("SELECT * FROM events WHERE event_date >= CURRENT_DATE()");
CURDATE()
:$db->query("SELECT * FROM events WHERE event_date >= CURDATE()");
$db->query("SELECT * FROM events WHERE event_date >= CURRENT_DATE()");