srand((float) microtime() * 10000000);
$banner = array (
	"Banner01.jpg", "Banner02.jpg", "Banner03.jpg", "Banner04.jpg", 
	"Banner05.jpg", "Banner06.jpg", "Banner07.jpg", "Banner08.jpg", 
	"Banner09.jpg", "Banner10.jpg"
);

$rand_key = array_rand($banner);

$filename = $banner[$rand_key];

echo "<img src='$filename'>\n";