Ejemplo con Jquery me dice si tiene alguna duda.
<?php
$arrayImg[] = array("urlImg" => 'img_file/imagen_thumbs/img4e493fa80bd3452QIFW.jpg');
$arrayImg[] = array("urlImg" => 'img_file/imagen_thumbs/img4e493fa80bd3452QIFW.jpg');
$arrayImg[] = array("urlImg" => 'img_file/imagen_thumbs/img4e4c9d68705bbBGWK40.jpg');
$arrayImg[] = array("urlImg" => 'img_file/imagen_thumbs/img4e493fa80bd3452QIFW.jpg');
$arrayImg[] = array("urlImg" => 'img_file/imagen_thumbs/img4e4945168f954BBPG02.jpg');
?>
<!DOCTYPE html>
<html>
<head>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.6.2/jquery.min.js" type="text/javascript"></script>
<script type="text/javascript">
<?php
echo "array_imagen = new Array(".count($arrayImg).");\n";
while (list($key, $arrayInfoImg) = each($arrayImg)) { ?>
array_imagen[<?php echo $key;?>] = '<?php echo $arrayInfoImg["urlImg"];?>';
<?php
}
?>
var countImg = 0;
function cambiarBanner(){
$("#banner").attr("src",array_imagen[countImg]);
countImg ++;
countImg = countImg % array_imagen.length;
setTimeout("cambiarBanner()", 4000);
}
$(document).ready(function(){
cambiarBanner();
});
</script>
<title></title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
<img src="" id="banner">
</html>