PHP Code
/* PHP CODE HERE */

$Ads = array (
	'http://www.germanshepherdhome.net/testadbanner1.jpg',
	'http://www.germanshepherdhome.net/testadbanner2.jpg',
	'http://www.germanshepherdhome.net/testadbanner3.jpg'
	);


/* BODY HERE */
$body = <<<EOF
 $Ads[mt_rand(0, count($Ads)-1)]
EOF;

might work

Remember array index starts from 0 there wink

Also, i'd recommend (if i were you) to put your banners in something like /forums/images/banners directory. That way you don't clutter up your site's root dir.. if you do, you'd need to modify the URLs above, but you get the drift smile