Why changes in php files suddenly stop showing until reboot (Apache2 server, browser cache disabled)?

Question

PHP

I edit the files of the local site, refresh the page and see the changes, but after a while the next changes are no longer displayed, no matter which file they are made to. It's not about the browser cache, as I disable it during development. Tried disabling opcache in php.ini - didn't help. Restarting the computer helps (I did not try to restart only Apache via service apache2 restart). The server configuration is as follows:
OS: Ubuntu 16.04
PHP: 7.1.6
Apache: 2.4.18 with default settings
What could be the problem and how to solve it?

Answer 1

Opcache badly tried to disable, apparently.