When you face an error Uncaught RedisException: Permission denied in your PHP code, you will need to check if that is working normally in the command line but happening in the web page. If it is, that is 100% caused by your linux security policy. In that case, you will need to turn SELinux policy off that located at /etc/selinux/config.
The followings are the example of Uncaught RedisException: Permission denied error
You can get information to disable SELinux policy at http://qsok.com/display/KB/Turn+SELinux+off+on+CentOS