Allow multiple word classes with a -

[aubreypwd]

class-app.php#L112

Here, if you create a class like, Edit_Posts you have to create a file like class-edit_posts.php which should be class-edit-posts.php.

$file = 'class-' . strtolower( str_replace( '_', '-', end( $parts ) ) ) . '.php';

...is better.