How to put this in the menu

[Snakehill]

I made this little screen scrape to see how many users there are in my (external) Videochat:

PHP Code:

<?php
$url = 'http://www.mtgstream.com/online_amount.php';
$output = file_get_contents($url); 
echo $output; 
?>

The link to the Videochat in the header-template is:

<td>
<a href="http://www.magiciansthegathering.com/forums/chat.php">Videochat</a>
</td>

I would like to put the PHP in there so it shows up like 'Videochat (4)' with the '4' being the amount of users in the chat. I know how to put the brackets around the PHP but I can't just copy/paste the PHP in there because the number simply won't show up.

So how do I do this?

Thanks in advance!