I close brackets that have been opened- that’s tidy and the correct thing to do, right?

Apparently not for PHP files- The recommendation is that you miss off the final ?>

Why? Because whitespace at the end of the file may be sent to the browser, and header() declarations then won’t function properly.

This is the kind of tip you pick up on quickly if you work in a team, but miss out on if you’re solo!
Thanks onion2k.