SELinux setting greatly depend on which exact setup you are running. E.g. when installing Cacti into /var/www/html/cacti (which is the default installation location), the web server httpd usually has the required permissions to execute as required. But when e.g. installing into a private directory, e.g. ~/mycacti, you will have to provide specific SELinux settings.

This is an excerpt from my personal settings when installing into private directory. Any or all of them may be obsolete, when using the default location.

/usr/sbin/setsebool httpd_read_user_content=1
/usr/sbin/setsebool httpd_tty_comm=1
/usr/sbin/setsebool httpd_can_network_connect=1
/usr/sbin/setsebool httpd_builtin_scripting=1
/usr/sbin/setsebool httpd_enable_homedirs=1
/usr/sbin/setsebool httpd_enable_cgi=1

In case you are using BOOST server network setup, it was reported that

/usr/sbin/setsebool httpd_can_network_connect=1

has to be set.