Zabbix 3.0 requires PHP 5.4 or above and is consequently not officially available in base RHEL/CentOS 6 repositories.
To run Zabbix 3.0 with MariaDB 10.1 and PHP 5.6 (php56u), I built packages for EL6 on Fedora COPR:
COPR: ritz/zabbix30
These RPMs are built for Zabbix 3.0.1 linked against MariaDB 10.1.x and PHP 5.6.19.