reflect the list without refreshing the page in php - php

Question

I am trying to show the list of online users in my application. Let me explain my requirement.
I have a Mysql DB table where list of username and their status mode(either 1 or 0) are storing. I have two php pages. One is for listing down all user's name and the status mode. Second page is for editing the mode of users from 1 to 0 and vice versa.
Now I open these two pages from different system. If I change the status of one user(edit page) from one system then automatically it will reflect to the another system, where the listing page is opened, with the updated record and obviously this should happen before refresh the listing page. The same like gtalk chat users.
I am not asking the code, but please help me how to proceed to resolve the issue. Obviously, cronjob is one of the solutions, please provide another solution.
Thanks in advance.

Answer 1

Well cronjobs are in fact not the thing you need.
With cronjobs you can schedule a task. What you want is client side refresh when new info is found. While cronjobs are server side and always on an interval.
What you need is polling or commet
The first, polling, you use your client side to execute a script every x seconds and look if there is new info (waste of resources in my opinion).
Commet, is now a days a better solution. But often hard to implement. I used pusher for this type of stuff. You can push messages to (all) clients connected and say there is new info. And then they will update or with the message comes also the new info

Answer 2

To achieve something like this, you should use JavaScript and Ajax in the clientside.
Give the XMLHttpRequest a try. To make it easier you could use something like jQuery.
On the serverside you could use json to transmit the data.
Read the data from the table and put it into an array, let's call it users, the keys are the names and the values are their mode(1 or 0).
Then use json_encode(ARRAY):
//Echo the results in json format
echo(json_encode($users));
Let's say, the users 'Frank', 'Susan' and 'George' are online and 'Isabell' and 'John' are offline. Then the script would result in an output similar to this:
{"Frank":1,"Susan":1,"George":1,"Isabell":0,"John":0}
Of course you need to put this and the loading into another php-script, maybe refresh.php.
And, to read the data from the script, add some JavaScript to your view page.
Use the XMLHttpRequest to request data from the script you just added.
Or, if you use jQuery, you can simply use $.getJSON("NameOfTheScriptYouJustWrote") which returns an already parsed object.
Then use the returned data to update the list of users. And refresh it every 5-20 seconds.
And keep in mind that this is not an efficient way at all and that this will not work well if there are many clients using your service.