<img src="/img/banner<?php echo rand(1,3); ?>.jpg" alt="">

<?php 

/* files to rotate */
$files = array('aaa.gif','bbb.gif','ccc.gif','ddd.swf','fgtr.swf');

/* current file */
$file = isset($_COOKIE['file']) && in_array($_COOKIE['file'],$files)?$_COOKIE['file']:null;

/* remove previous file shown */
if($file !== null) {
	$filesIndex = array_search($file,$files);
	array_splice($files,$filesIndex,1);
}

/* choose a new file to show */
$filesIndex = array_rand($files,1);
$file = $files[$filesIndex];

// save file to cookie
setcookie('file',$file);

// get the files extension to determine how to show it
$filesExtension = strrpos($file,'.') === false?'':substr($file,(strrpos($file,'.')+1));

// alternate display implementation for an image and swf
switch($filesExtension) {
	case 'swf':
		echo "<p>Showing Flash: $file</p>";
		break;
	
	default:
		echo "<p>Showing Image: $file</p>";
}
?>