setInterval doesn't seem to re-execute php script - php

Question

what i'm trying to do is get a variable to update every 5 seconds doing this:
setInterval(document.getElementById("listeners").innerHTML =
"<?php include('../includes/shoutcaststuff.php');
echo $dnas_data['CURRENTLISTENERS']; ?>",5000);
but what happens is the inner html is set but doesn't update every 5 seconds like it should.
my guess is that the php only executes once, but i have no idea if that's the case or not.
and i'm aware i should make a function to do the stuff inside setInterval... i'll clean up the code once i figure out how to make it work.
thanks in advance.
ok... ajax was 'the best' answer since no more than 2 people would be logged in at a time here so server requests isn't such a big deal.
here's how i got it to work:
function lCount(){
$.get("../includes/shoutcaststuff.php",{Count: "TRUE"}, function(data){
document.getElementById('listeners').innerHTML = data;
});
}
setInterval(lCount,5000);
and added this to the end of the php:
if(isset($_GET["Count"])){
echo $dnas_data['CURRENTLISTENERS'];
}
now it works fine.
thanks for the suggestions guys :)

Answer 1

<?php include('../includes/shoutcaststuff.php');
echo $dnas_data['CURRENTLISTENERS']; ?>
This code only executes once when the page is built. For the rest of the times this javascript is called whatever is first echoed will be the value.
Instead of using a static value here, you are going to need to use an ajax request (or a websocket if you want to use html5). The request will then hit your server once every 5 seconds. Keep in mind that this can cause undue load on your server.
Ratchet is a commonly used PHP WebSocket implementation that allows for data to be sent to the client using push technology. This is probably more preferable than using your polling approach.

Answer 2

PHP code is run on the server generating the HTML/JS. Use ajax if you need to run php code once the page has loaded.
Take a look at this for example;
Using this:
setInterval(document.getElementById("listeners").innerHTML =
"<?php echo "1";?>",5000);
Will output this to the browser:
setInterval(document.getElementById("listeners").innerHTML =
"1",5000);