Anytime you make a change to items such as php.ini, you will need to restart your web server (httpd). FYI: httpd = http daemon. On our CentOS servers this generally Apache, but could be something else, particularly if you are using LXAdmin as your webhost manager.
For those using our managed servers with root access, here are the commands to do it from the command line:
to restart:
/sbin/service httpd restart
to start:
/sbin/service httpd start
to stop:
/sbin/service httpd stop