You could use an iframe or AJAX. Using iframe is easiest. Make up a php file called display_counter.php and put the php code on it:
Then on your HTML page have an iframe:Code:<?php echo file_get_contents('path/to/counter.txt');?>
You could even skip the step of the intermediate php page and just do:Code:<iframe name="counter" src="display_counter.php" width="90" height="30" scrolling="no" frameborder="0"></iframe>
But sometimes displaying a text file in an iframe can fail. If you rename it to counter.htm (make sure to also change wherever it's referenced in the other code, so it gets updated), then there should be no problem.Code:<iframe name="counter" src="path/to/counter.txt" width="90" height="30" scrolling="no" frameborder="0"></iframe>
Using AJAX for this is complicated, and really a bit of overkill for such a simple piece of information unless you already have jQuery on the page, in which case it's fairly simple to load the contents of the counter file into a div element on the page. Again, it would be best if it were a .php or .htm file, but probably less critical than with iframe.

