Thanks Gizmo,
I do have it all in a file called AdRotation.php
The file is in the forum/ directory.
I don't know the correct syntax to pull it in though.
In a standard .php page it would be like this (but this doesn't work).
/* PHP CODE HERE, IF NECESSARY */
/* DO NOT CHANGE THE LINE BELOW */
$body = <<<EOF
<?
include_once("AdRotation.php");
echo "<div align='center'>$bannerAd</div>";
?>
EOF;
/* DO NOT CHANGE THE LINE ABOVE */
