This is a class adapted from the old Illuminate\FileSystem\ClassFinder class that was in the Laravel source once upon a time.
Call ClassFinder::findClasses($path) to obtain a list of fully qualified class names from the given directory.
By default this will match any file with an extension of .php, but a second optional parameter can be passed in to provide a different matching pattern (eg *Service.php)
If the directory is potentially non-existent, ClassFinder::findClassesSafely($path) can be called, which will return an empty array if the directory does not exist.
A fully qualified class name for a single class may also be obtained through ClassFinder::findClass($pathToClass)