A regular "phpinfo()" or a call to "var_dump( get_loaded_extensions() );" in a web page clearly indicates that opcache is not loaded. Apparently, the issue is in /etc/php/apache2-php7.0/ext-active/opcache.ini Instead of: zend_extension=/usr/lib64/php7.0/lib64/opcache.so The following works: zend_extension=opcache.so This is a bit strange to me since it works in CLI mode without that change: "php -i" shows Zend Opcache while having the full path to the so file.
It appears I still had a libphp7.so that came from a manual compilation of PHP7. Cleaning my environment to use the one from portage resolve that (non-)issue. Additionally, using "zend_extension=opcache.so" did NOT work anymore once the correct libphp7.so was used, I had to turn back the full path again.
