Java PHP中基于时间的代码执行

Question

I have a web application in PHP and Javascript where i want to apply a time based question generation. I have preset of code that will be executed at a specific time which will generate the question.

Now i am thinking that how can i apply this. Here are some the information regarding the web

1. Web is running on wamp server and there are almost 100 users used it regularly (every day). They login in the website two time between 9-11am and 2-6pm.
2. The question geneartion time should be at 4pm.

Now, i can make use SetTimeOut and Javascript Date object in order to acheive the desire functionality: Here

    function checkVotingQuestionTime()
    {
     var currentTime = new Date();

     if(currentTime.getHours() >= 16 && currentTime.getHours() < 23)//check the time from user OS
     {
            checkVoteQuestionGenerated();
     }
    }
    function checkVoteQuestionGenerated(){

    //query to php check question exists
    //if no 
    //then generate question

}

And Register it at document ready event in main page(after login). This code will be open for all users.

$jq(document).ready(function() {
setInterval(checkVotingQuestionTime, 60000);
}

As it appear that, this is not feasible code, because

1. It will be run from every client (set timeout and server hit regularly and if i also get time from server than it will more often hit on server)
2. A user can change the system time to run above code.
3. Multiple question can be generated if two clients simultaneously check that the question is not generated so generate the question.

So how can I control above limitations or is there any other proper solution available?

Answer 1

Having 100 clients poll the server every few minutes is not a big deal. Every time they open a page on your website that's in effect polling the server. So moving the date check to php on the server side is the best solution for what you have currently set up.

If you don't like the idea of having the client poll the server every now and then for aesthetic reasons (and I can appreciate that), for example you want the question to be refreshed at 16:00 on the dot, you could look into using a sockets. This, in effect, means the client is listening to any changes sent from the server, without the need to poll it, and updates when necessary.

Socket.io is easy to use, but not the simplest when it comes to interfacing with php. I don't know if you're familiar with Node.js but here's a small discussion some others had regarding sockets and php:

What is the best way to use websockets along with PHP and MySQL scripts?