<?php
class MySessionHandler implements SessionHandlerInterface, SessionUpdateTimestampHandlerInterface {
    public function write($sessID, $sessData, $lock = false): bool {
        if(...){
            return false;
        }

        if(...){
            return false;
        }
        return true;
    }

    public function updateTimestamp($sessID, $val){
        return false;
    }
}

$handler = new MySessionHandler();
session_set_save_handler($handler, true);
session_start();