php closes the browser and the program continues execution

set_time_limit(0);
        ignore_user_abort(true);
        $i = 0;
        while ($i ++ < 200) {
            email('1952321910@qq.com', 'dgd', 'weq', '定时任务提醒');
            sleep(3);
        }  

The above introduces PHP to close the browser and the program continues to execute, including the content. I hope it will be helpful to friends who are interested in PHP tutorials.