Cleanup image file names in a directory

<?php
    //traverse a directory of images and clean up the filenames
    $image_dir = '/path/to/dir/';

    if($handle = opendir($image_dir)){
        while(false !== ($file_name = readdir($handle))){
            if($file_name == '.' || $file_name == '..'){ continue; }
            preg_match('/(.*)(\.\w+)$/', $file_name, $matches);
            $image_name = $matches[1];
            $image_extension = $matches[2];

            $new_name = preg_replace('/\-{2,}/', '-', preg_replace('/\W/', '-', strtolower($image_name)));

            rename("{$image_dir}{$file_name}", "{$image_dir}{$new_name}{$image_extension}");
        }

        closedir($handle);
    }

?>