Your using the randomization tutorial from ethics designs I see. Their ending code looks like this
<?
$banner[] = "<a href=\"URL\" target=\"_blank\"><img src=\"IMAGE\" alt=\"\" border=\"0\" width=\"88\"
height=\"31\"></a>";
$banner[] = "<a href=\"URL\" target=\"_blank\"><img src=\"IMAGE\" alt=\"\" border=\"0\"></a>";
echo $banner[array_rand($banner)];
?>
Are you including this onto a page? Because it sais to do so in their tutorial I would do something like this.
<?
$banner[] = "<a href=\"URL\" target=\"_blank\"><img src=\"IMAGE\" alt=\"\" border=\"0\" width=\"88\"
height=\"31\"></a>";
$banner[] = "<a href=\"URL\" target=\"_blank\"><img src=\"IMAGE\" alt=\"\" border=\"0\"></a>";
echo $banner[array_rand($banner)];
Then
<?
include "file.php"
echo $banner[array_rand($banner)];
?>