Strange problem - caching?

I have upgraded my OS to Ubuntu 13.10. I’ve used Wordpress and Roots quite a bit and have never seen this particular problem before.

When I change PHP files (for instance renaming footer widget area in /lib/widgets.php) none of the changes take affect. It’s like the PHP is cached somewhere, even if I comment out lines in functions.php it has no effect. I’ve checked the PHP files have been changed in three text editors just to make sure.

This is on a latest WP install 3.7 with Roots theme working perfectly (other than not being able to edit) on Apache2.

Anybody got any ideas? Is there something new in 3.7 caching wise?

Many thanks,

Gwilym

Well - web development is always an adventure. Restarted my computer twice and this cleared it up. Must have been an Apache weirdness…