Images in Directory

Ok I have a program which stores all the images in a give directory in a array. I need to make sure that the array has no other files like text files or thumb.db. How can I filter out everything except image files?
Can this also be use to instead of image to use for folders also?

 

<?php

// This would be the array you got from your "images in the directory" function
$files = array("thing.gif", "another.jpg", "somethingelse.jpeg", "shouldnotbehere.txt", "yetanother.png", "thumbs.db", "more.bmp");

$files = array_filter($files, "imageOnly");
echo "<xmp>";
print_r($files);
echo "</xmp>";

function imageOnly($input) {
   return preg_match('/\.(gif|jpe?g|png|bmp)$/', $input);
}

?>

PHP:

For that you would do:

$files = array_filter($files, "is_dir");

PHP:

 

OK, cool, just have one more question. How do I do a case insensitive comparison?
Iam trying to sort the array, but the cases of the files change the order.

 

natcasesort($files);

PHP: