Problem with using AJAX

[MP3]

I'm confused about how to connect between Java scripts and PHP file to show some data in my forum.

For example I will create new PHP file and name it mp3.php inside this file it will check certain variable, if it's satisfy the requirement then a short sound will play.

Now, the important point how to us AJAX to run this PHP file for each 5 min inside my forum? And let's say I want to insert the AJAX in my forum header so the sound will play for any member in and page.

Is it possible? And if it's possible how can I do it?

[calorie]

Check out the AJAX tutorial here.

[MP3]

Calorie, I checked many topics about AJAX but I didn?t find what I'm looking for.
I have a PHP file, simply I add a sample if condition:

PHP Code:

<?php

require_once('./global.php');

$a = $db->query_first("SELECT bb FROM " . TABLE_PREFIX . "aa WHERE `id`='1'");


if ("$a"=="3")
{
        $play = "<embed src=\"anything.wav\" autostart=true hidden=true></embed>";
}
else
{
        $play="";
}
?>

Now I want to insert the AJAX to my forum header to check the PHP file every 5 min when the condition exist then a small popup will show up without manually refresh. Can you help me?