$today = new DateTime();
    $alert_date = new DateTime($alerts[$i]['due']);

    $interval = $today->diff($alert_date);

    if($interval->d > 0) {
        $deadline = $interval->format('%d') . ' days';
    } elseif($interval->m > 0) {
        $deadline = $interval->format('%m') . ' months';
    } elseif($interval->y > 0) {
        $years = $interval->format('%y') . ' years';
    }