If you're on Windows then case doesn't matter, and even if it did this feels like an abuse of glob(). Tokenizing by slash and recursively scandir()ing makes more sense to me.

It's true that PHP's glob() limits the pattern to MAXPATHLEN characters when this doesn't quite make sense - with features like [] and {} the pattern can certainly be longer than the filenames it would match. So perhaps that check should be dropped.

Regardless, on my Win 10 PHP 7.1 the (PHP_)MAXPATHLEN is 2048 and your code runs fine. What SAPI (eg, php-fpm, cli) are you running this from, and did you get PHP from windows.php.net or somewhere else?

I need a safe and reliable way to determine the true casing of a file name. On Linux it's easy, spell it as it is or you won't find it. Windows is more tolerant, accepting anything you throw at it. But that also means that my pages are accessible through a number of different URLs. I need my pages to be accessible on exactly one URL, so I'm correcting the spelling to the true file name. On Linux, this also allows me to accept different casing but redirect the user to the correct name.

I'm running XAMPP with Apache and PHP on Windows. It uses mod_php. I haven't tested this on Linux yet, that would be an Ubuntu 16.04 system with its default PHP packages and FastCGI.

Like @requinix already stated, the maximum allowed pattern length
is 2048 as of PHP 7.1.  I do not see the need to extend this.

> I do not see the need to extend this.

I still don't see that.