Started getting the following error while running ./validate.php for LibreNMS
Cannot load Zend OPcache - it was already loaded
Looks like the problem arises out of PHP trying to load two ini files for OPcache. Was trying to enable OPcache for LibreNMS so I created an opcache.ini file and put the settings in it. I missed the default 10-opcache.ini file.
Moving all the settings into the 10-opcache.ini file and deleting the created opcache.ini file resolved the issue for me.